Caramelized Onion and Tomato Tart Au Gratin is absolutely A-M-A-Z-I-N-G!!! This delicious side dish includes lots of caramelized onions in a homemade pie crust. It’s topped with four cheeses! It’s layered with sliced tomatoes, several delicious herbs and has more cheese on top. Spectacular is about the only word worthy of this fabulous tomato tart recipe. My mouth is watering just thinking about the awesome texture and flavors of this tomato and onion pie.

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Some of you follow me on Pinterest. Last week I pinned 20 or 30 different tomato tart recipes. I was trying to find one that I really wanted to try. I began seeing all these wonderful looking pictures of tomato tarts online. Finally I landed at this recipe, based on Ina Garten’s Tomato and Goat Cheese Tart. I liked several things from this recipe. Even though I had goat cheese on hand, I chose not to use it. Neither did I want to use the mayonnaise-dijon mustard combo I had seen in other recipes.

I took the idea for the caramelized onions from these two recipes. The idea of setting the tomatoes out on the counter to dehydrate for an hour came from Milk Glass Kitchen’s rendition. I used some of their seasonings, but departed completely from some of their other ingredients. Instead I used Asiago, Parmesan, and Fontina cheeses on the tart underneath the tomatoes. I used Pecorino Romano cheese on the top after I’d seasoned the tarts. All I can say about this tart is that the taste was fantastic.

It does take a few minutes to whip up a homemade pie crust. (For me, it takes about 5 to 10 minutes depending on how many crusts I’m making at one time). But you can substitute store bought pie crust if you don’t have time. The tomatoes need to be sliced, salted and set out on paper towels for at least an hour to drain. This helped the pie not become soupy.

The longest thing for me to do was caramelizing the onions. It seemed to take FOREVER! To my chagrin I’ve never caramelized onions before. I was afraid to have my heat too high and scorch them. As a result they probably took about one and a half hours before it was all said and done! Perhaps because I was doing two batches. Everyone else says you can do it in about 45 minutes. Be prepared for them to take a while to cook. This site was the most helpful in learning how to caramelize onions for the first time.

Here are a few of my recommendations: First, after you make the pie crust, set it aside and don’t put ANYTHING into the pie shell until you have all the components ready. If you allow the onions, cheeses, or tomatoes to sit in the pie for any length of time before baking, you will end up with a soggy crust.

This is the same for making fruit pies. Don’t allow the fruit mixture to sit in an unbaked pie shell for more than a minute or two before tossing the pie into the oven if you don’t want a soggy crust. Truthfully, you are better off getting everything else ready first, THEN make your pie crust. That way your pie crust won’t dry out while you’re getting everything else ready.

Second, caramelize the onions when you have plenty of time. You can even do these the night before and stir occasionally while you’re watching TV. Then store them in a refrigerator until ready to use. At your earliest opportunity, on the day you want to make the tart, slice the tomatoes. Then set them out on paper towels to drain, being sure to salt them generously. It doesn’t matter if they set out a few hours before you have time to get around to them. Just get them draining on the counter until you’re really ready to make the recipe.

You will be amazed at how much liquid will drain from the tomatoes. I made three different types of tarts at the same time. So I had tomatoes, heirloom tomatoes, grape tomatoes and zucchini all sitting out at the same time. There was probably a cup of liquid run-off from all of the stuff I did!

When you’re ready to assemble the tart, do this. Lay the caramelized onions in the bottom of the uncooked pie crust. Sprinkle three of the four cheeses over top of the onions. Place tomatoes over top of the cheeses in overlapping fashion. Sprinkle the tomatoes with all the seasonings. Then top everything with the pecorino romano cheese. As soon as you finish assembling all the ingredients, the tart/pie should go into the oven. It goes without saying that you need to have a preheated oven!

If you’re looking for a great new way to use up garden tomatoes or onions, then by all means consider this recipe. Just be prepared for the fact that it may take a few hours to get it all done from start to finish. Even still, you will sink your teeth into one of the most delicious, tantalizing tomato tarts you have EVER tasted. Caramelized Onion and Tomato Tart Au Gratin is the real deal! Oh, my, it’s one of those recipes I think I could eat almost every day! This healthy, low calorie, and tasty tart is excellent served as a side dish, but I also ate it as a main dish. Add a salad or bread, and it is yum, yum delicious. It’s also wonderful for breakfast. On top of that it reheats well to serve for leftovers.

Caramelized Onion and Tomato Tart Au Gratin is one of the BEST tasting tarts you will ever eat.

This scrumptious tart recipe is sweetened a little by the caramelized onions.

The savory blend of cheeses adds depth to a very rich tasting tomato tart. Caramelized Onion and Tomato Tart Au Gratin is a bit of work, but it’s SO worth it in the end! I served this first-try recipe to company and everyone loved it.

Here’s what I did.

Start with a batch of my Homemade Pie Crust recipe. I started out with 3 cups of flour (honestly, I don’t measure much, I go by texture, look, and feel), and that was enough crust to make 2 large torte pans like this, plus about 15-18 small miniature tart dishes.

Cut off the edge (and used all the leftover pieces for the small miniature tart dishes).

This is what the tart dish looks like after fitting it with crust. This tart dish is not as deep as a normal pie plate. Honestly, it is better for you to make up all the other ingredients and have them ready before making your pie crust. You don’t want your pie crust sitting out too long and getting dried out.

Slice onions and separate into rings. Place some olive oil in a skillet over medium heat and begin sauteing onions. Continue sauteing onions.

After about a half hour, add salt, pepper, thyme, and white wine vinegar or white wine. It took forever for my onions to caramelize.

I’m not sure if my heat was too low or I was stirring them too frequently. After cooking them an hour and a half I had to get going with the rest of the recipe so it would be ready on time for dinner.

Slice down tomatoes and set on paper towels. Generously sprinkle with salt. Allow the tomatoes to drain (dehydrate) at least one hour. Mine were laying out about three hours before I got around to them.

Once all your ingredients are ready start piling them into the pie shell. Spread caramelized onions over the bottom of your pastry shell.

I used these cheeses.

Sprinkle parmesan cheese over top of the onions. 

Now sprinkle with Asiago cheese.

Sprinkle with Fontina cheese.

Layer tomatoes in an overlapping fashion to completely cover the tart dish. 

I used these seasonings to spice the dish.

Sprinkle tomatoes with rubbed (not ground) sage, rosemary, oregano and basil. I grabbed two or three pinches and crushed the leaves in between my thumb and fingers a little bit before adding on top. It was probably at least 1/2 tsp. of each seasoning. Use more if you like a lot of seasoning on your tomatoes! 

Sprinkle with finely grated pecorino romano cheese. 

Bake at 350 about 20-30 minutes until tomatoes are tender and crust is lightly browned. Here’s what my tart looked like just out of the oven.

Caramelized onions and tomatoes are a wonderful combination. Then when you add all the cheese and seasonings – WOW! This recipe just pops with flavor. Even the kids enjoyed this tasty tomato tart recipe. 

This spectacular Caramelized Onion and Tomato Tart Au Gratin is a great pie to use up garden veggies like tomatoes or onions.

You can also refrigerate or freeze the tart and reheat it for later. (I froze some of them and reheated the tarts the following week for additional company).

This is a terrific side dish for dinner or as a breakfast entree. It’s especially nice for holiday meals.

Here’s the recipe.

CARMELIZED ONION AND TOMATO TART AU GRATIN

(Recipe inspired from Milk Glass Kitchen which is no longer a viable blog, source: inspired from Ina Garten)

Caramelized Onion and Tomato Tart Au Gratin

Teresa Ambra

This amazing vegetable pie has spectacular flavors using four different cheeses, tomatoes and caramelized onions. A fabulous Meatless Mondays recipe. It's also terrific as a side dish or for breakfast. Uses Parmesan, Asiago, Fontina and Romano cheeses. Even kids enjoy this fantastic tomato pie recipe.

No ratings yet

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 30 minutes mins

Total Time 45 minutes mins

Course Breakfast, Side Dish, Vegetable Pie

Cuisine American

Servings 8

Calories 243 kcal

Equipment

• 1 10-inch tart dish or pie plate
• 1 sharp knife to cut vegetables
• 1 large skillet
• 1 wooden spoon
• 1 spatula
• measuring cups
• measuring spoons

Ingredients

  

1x2x3x

• 1 extra large onion sliced and separated into rings, about 1-lb. or two large onions
• 2 tbsp. olive oil
• 3 tbsp. white wine vinegar
• 1/2 tsp. dried thyme
• 1/2 tsp. sea salt or Kosher salt
• 1/4 tsp. ground black pepper
• 3 large tomatoes sliced
• 1/2 cup parmesan cheese shredded
• 1/2 cup asiago cheese shredded
• 1/2 cup fontina cheese shredded
• 1/4 to 1/2 cup pecorino romano cheese finely grated
• 1/2 tsp. dried basil
• 1/2 tsp. dried oregano
• 1/2 tsp. dried rosemary crushed
• 1/2 tsp. dried rubbed sage leaves
• 1 recipe for single crust plain pastry

Instructions

 

• Slice tomatoes and lay out on paper towels.
• Sprinkle very generously with salt and allow to set out on counter and drain for at least one hour.
• Add olive oil to a large cast-iron or other skillet and heat over low to medium heat.
• Add onions and cook about 30 minutes turning occasionally so onions don’t burn.
• Add thyme, salt, pepper, and white wine vinegar.
• Continue cooking another 15-30 minutes or however long it takes to caramelize the onions.
• You may need to add a little water so the onions don’t stick too much.
• Use a heavy-duty metal spatula to scrape onions from pan if necessary.
• Prepare pie crust and fit into a large 10-inch tart pan.
• When all the other ingredients are ready, layer the caramelized onions on the bottom of the tart pan.
• Sprinkle Parmesan, Asiago and Fontina cheeses over top of the onions.
• Add tomato slices overlapping the edges.
• Sprinkle tomatoes with basil, oregano, rosemary, and rubbed sage leaves.
• Then sprinkle pecorino romano cheese over top of all.
• Bake at 350 for about 20-30 minutes until tomatoes are tender and crust is done.

Notes

NOTE: Preparation time does NOT include time required to caramelize onions. That may take an additional hour!

 

 

NOTE: Preparation time does NOT include time required to make pie crust.

 

 

NOTE: Do not start adding things to the pie shell until you have everything ready and it's ready to go into a preheated oven. Otherwise, you will end up with a soggy pie crust.

 

 

NOTE: You must lay out the tomatoes on the counter and salt them down so they drain, otherwise you will have a very mushy, juicy pie.

 

Recipe inspired from Ina Garten, the Barefoot Contessa via Food Network.

 

^© Can’t Stay Out of the Kitchen

Nutrition

Calories: 243kcalCarbohydrates: 17gProtein: 9gFat: 15gSaturated Fat: 6gPolyunsaturated Fat: 1gMonounsaturated Fat: 7gCholesterol: 23mgSodium: 611mgPotassium: 206mgFiber: 2gSugar: 2gVitamin A: 312IUVitamin C: 7mgCalcium: 262mgIron: 2mg

Keyword breakfast, cheese, onions, side dish, tomatoes

Tried this recipe?Let us know how it was!

Doesn’t Caramelized Onion and Tomato Tart Au Gratin look delicious? This fantastic tart is sure to tantalize your taste buds! You know a recipe’s a hit when little children love it!

I’m starting to drool over those caramelized onions. They added so much flavor to the recipe. 

Our family and company really enjoyed this version of Caramelized Onion and Tomato Tart Au Gratin. Because I didn’t add the ingredients to the pie crust until right before baking, the crust came out wonderfully. No soggy crust! Inhale, exhale, now drool!

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Caramelized Onion and Tomato Tart Au Gratin

Teresa Ambra

This amazing vegetable pie has spectacular flavors using four different cheeses, tomatoes and caramelized onions. A fabulous Meatless Mondays recipe. It’s also terrific as a side dish or for breakfast. Uses Parmesan, Asiago, Fontina and Romano cheeses. Even kids enjoy this fantastic tomato pie recipe.

No ratings yet

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 30 minutes mins

Total Time 45 minutes mins

Course Breakfast, Side Dish, Vegetable Pie

Cuisine American

Servings 8

Calories 243 kcal

Equipment

• 1 10-inch tart dish or pie plate
• 1 sharp knife to cut vegetables
• 1 large skillet
• 1 wooden spoon
• 1 spatula
• measuring cups
• measuring spoons

Ingredients

  

1x2x3x

• 1 extra large onion sliced and separated into rings, about 1-lb. or two large onions
• 2 tbsp. olive oil
• 3 tbsp. white wine vinegar
• 1/2 tsp. dried thyme
• 1/2 tsp. sea salt or Kosher salt
• 1/4 tsp. ground black pepper
• 3 large tomatoes sliced
• 1/2 cup parmesan cheese shredded
• 1/2 cup asiago cheese shredded
• 1/2 cup fontina cheese shredded
• 1/4 to 1/2 cup pecorino romano cheese finely grated
• 1/2 tsp. dried basil
• 1/2 tsp. dried oregano
• 1/2 tsp. dried rosemary crushed
• 1/2 tsp. dried rubbed sage leaves
• 1 recipe for single crust plain pastry

Instructions

 

• Slice tomatoes and lay out on paper towels.
• Sprinkle very generously with salt and allow to set out on counter and drain for at least one hour.
• Add olive oil to a large cast-iron or other skillet and heat over low to medium heat.
• Add onions and cook about 30 minutes turning occasionally so onions don’t burn.
• Add thyme, salt, pepper, and white wine vinegar.
• Continue cooking another 15-30 minutes or however long it takes to caramelize the onions.
• You may need to add a little water so the onions don’t stick too much.
• Use a heavy-duty metal spatula to scrape onions from pan if necessary.
• Prepare pie crust and fit into a large 10-inch tart pan.
• When all the other ingredients are ready, layer the caramelized onions on the bottom of the tart pan.
• Sprinkle Parmesan, Asiago and Fontina cheeses over top of the onions.
• Add tomato slices overlapping the edges.
• Sprinkle tomatoes with basil, oregano, rosemary, and rubbed sage leaves.
• Then sprinkle pecorino romano cheese over top of all.
• Bake at 350 for about 20-30 minutes until tomatoes are tender and crust is done.

Notes

NOTE: Preparation time does NOT include time required to caramelize onions. That may take an additional hour!

 

 

NOTE: Preparation time does NOT include time required to make pie crust.

 

 

NOTE: Do not start adding things to the pie shell until you have everything ready and it’s ready to go into a preheated oven. Otherwise, you will end up with a soggy pie crust.

 

 

NOTE: You must lay out the tomatoes on the counter and salt them down so they drain, otherwise you will have a very mushy, juicy pie.

 

Recipe inspired from Ina Garten, the Barefoot Contessa via Food Network.

 

^© Can’t Stay Out of the Kitchen

Nutrition

Calories: 243kcalCarbohydrates: 17gProtein: 9gFat: 15gSaturated Fat: 6gPolyunsaturated Fat: 1gMonounsaturated Fat: 7gCholesterol: 23mgSodium: 611mgPotassium: 206mgFiber: 2gSugar: 2gVitamin A: 312IUVitamin C: 7mgCalcium: 262mgIron: 2mg

Keyword breakfast, cheese, onions, side dish, tomatoes

Tried this recipe?Let us know how it was!