Optional toppings: Shredded lettuce, chopped tomatoes and reduced-fat sour cream
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 1 tortilla, about 3/4 cup meat mixture and a scant 3 tablespoons cheese. Repeat layers 3 times. Cover and microwave on high until cheese is melted, 4-5 minutes. Let stand for 5 minutes before cutting. Serve with toppings if desired.