Preheat oven to 350 degrees. Spray a 9" x 13" baking dish with pan spray. Line the bottom of the dish with six tortillas (cut or tear as necessary to cover the area). Spread 1 can of tomatoes over the tortillas, followed by 1 cup ground beef or chicken, 1 cup beans, 1/2 cup of sour cream, 1/2 cup onions, and 3/4 cup cheese. Add another layer of tortillas and repeat the sequence of other ingredients. Add one more layer of tortillas and top with 1/2 cup cheese. Bake at 350 degrees for 45 minutes.