Preheat oven to 350 degrees F. Spray a large 13-inch by 9-inch baking dish with cooking spray and set aside.

In a bowl, stir together ground beef and taco seasoning. Add red pepper, green onions, and 1 cup of the cheese. Toss together.

In a separate large bowl, beat eggs, egg whites, and milk with a whisk until combined.

Place 3 tortillas in the bottom of your prepared casserole dish, tearing if needed to fit the bottom of the dish.

Top the tortillas with half of the beef mixture. Layer 3 more tortillas on top, then top those tortillas with the remaining beef mixture. Top that layer with the 3 remaining tortillas. Pour egg mixture over tortillas. Sprinkle remaining ½ cup of cheese on top.

Cover casserole tightly and bake for about 45 minutes, or until the center is set. Remove the cover and cook for an additional 5-10 minutes to allow the cheese on top to brown and crisp slightly.

Serve with salsa or diced tomatoes, sour cream, avocado, or guacamole.