Preheat the oven to 350°F (175°C).

In a large mixing bowl, combine the shredded chicken, black beans, corn, diced tomatoes, chili powder, cumin, garlic powder, salt, and pepper. Mix well.

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

Layer half of the tortilla quarters over the salsa.

Spread half of the chicken mixture over the tortillas, followed by half of the shredded cheddar cheese.

Repeat the layers with the remaining tortillas, chicken mixture, and top with the remaining cheese.

Pour the remaining salsa over the top of the casserole.

Cover the dish with aluminum foil and bake for 25 minutes.

Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.

Let the casserole cool for 5 minutes before serving. Top with sour cream and cilantro if desired.