In a large skillet, cook turkey over medium heat until meat is no longer pink; drain. Stir in the tomato sauce, minced onion, garlic powder, pepper and salt; heat through.
In a 2-1/2-qt. round microwave-safe dish coated with cooking spray, layer one tortilla, about 3/4 cup meat mixture and a scant 3 tablespoons cheese. Repeat layers three times. Cover and cook on high for 4-5 minutes or until cheese is melted. Let stand for 5 minutes before cutting. Serve with toppings if desired. Yield: 4 servings.