Preheat your oven to 350°F (175°C).
In a large skillet over medium heat, cook the ground beef or turkey until browned. Drain excess fat if necessary.
Stir in the black beans, corn, diced tomatoes, and taco seasoning. Cook for about 5 minutes until heated through.
In a 9x13 inch baking dish, layer half of the tortilla quarters on the bottom.
Spread half of the meat mixture over the tortillas, followed by half of the cheddar cheese.
Repeat the layers with the remaining tortillas, meat mixture, and cheese.
Cover the baking dish with aluminum foil and bake for 20 minutes.
Remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and golden.
Let the casserole cool for 5 minutes before serving. Top with sour cream, green onions, black olives, and cilantro if desired.