Preheat the oven to 350°. Spray a pie plate with nonstick cooking spray.
In a large skillet, brown the beef and onions until the meat is cooked through and the onions have turned clear, about 5 to 7 minutes.
Add the tomatoes, tomato sauce and seasonings and cook another 3 minutes.
Layer the tortillas, sauce, and cheese in the prepared baking dish.
Bake for 15 minutes until hot and the cheese is melted and bubbly.
If you like, serve wedges of the casserole with the toppings.
Notes
Promptly store leftovers in an airtight container in the refrigerator, for up to 3 days.Nutritional values are approximate and based on ¼ the casserole.