Brown beef and onion in large skillet until beef is no longer pink; drain.
Use a hamburger chopper to break meat down in small pieces while frying.
Add stewed tomatoes, sauce, taco seasoning and chilies.
Heat through.
Spray a 10x15” baking dish with cooking spray, then put about a half cup of the beef mixture on the bottom to keep flour tortillas from sticking.
Then layer tortillas, 1/5 of the beef mixture, sprinkle with about 1 cup cheese.
Repeat layers once.
Then layer tortillas, beef mixture and spoon the sour cream over all.
I just put really small dabs on. (Don’t use more than 1 cup as it won’t cook well).
Repeat with tortillas, beef and cheese two more times.
This makes 5 layers in all.
Bake, covered, about 25-30 minutes at 350°.