Preheat oven to 350F. In large skillet cook ground beed until brown and drain.
In large bowl, stir together oninon, enchilada sauce, tomato sauce, sour cream and chiles; mix well. Season to taste with salt or pepper.
Layer half the beef, tortillas, sauce mixture and cheese in lightly greased 3 quart rectangular baking dish. Repeat layers except for cheese. Bake, uncovered 40 mins; sprinkle remaining cheese over top and bake 5 mins more. Cut into squares to serve.