Preheat oven to 425º.
Place muffin liners in a 12-tin regular muffin pan and a 6-tin regular muffin pan.
Spray each liner with cooking spray; set aside.
In a large mixing bowl, combine flour, granulated sugar, baking powder, cinnamon and salt.
In a separate bowl combine egg, milk, butter and vanilla with a whisk.
Stir in apples.
Combine egg mixture with flour mixture and stir just until mixed.
DO NOT OVERMIX!
Spread batter into prepared muffin liners about ¼ to ½ full.
Place a caramel in center of each muffin.
Cover the muffin with more batter filling to almost the top of the muffin tin.
Sprinkle about two tablespoons of streusel topping over top of each muffin.
Bake at 425º for 5 minutes.
Reduce heat to 350º and continue baking an additional 15-19 minutes or until a toothpick inserted in center comes out clean.