In a large skillet over medium heat, add the ground beef. Cook until browned, breaking it apart with a wooden spoon, about 5-7 minutes. This step is crucial to develop flavor.

Drain any excess fat from the skillet. Add the taco seasoning, black beans, corn, and salsa to the skillet. Stir well to combine and let simmer for 5 minutes. This allows the flavors to meld together.

Preheat your oven to 350°F (175°C). This ensures even cooking.

In a 9x13 inch baking dish, spread a thin layer of the beef mixture on the bottom.

Layer 2 tortillas over the beef mixture, tearing them if necessary to fit.

Add half of the remaining beef mixture over the tortillas, followed by 1 cup of shredded cheese.

Repeat the layering process with 2 more tortillas, the rest of the beef mixture, and another cup of cheese.

Top with the final 2 tortillas and the remaining cheese.

Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes. This helps to melt the cheese and heat the filling.

Remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and golden brown.

Remove the casserole from the oven and let it cool for 5 minutes before slicing. This helps the layers to set.

Serve warm, topped with sour cream, chopped green onions, and sliced black olives.