01 - Preheat oven to 375°F. Lightly coat a 9x13 inch baking dish with cooking spray or vegetable oil.
02 - Combine shredded chicken, 1 cup enchilada sauce, black beans, corn, diced red onion, cumin, chili powder, garlic powder, salt, and pepper in a large mixing bowl. Mix thoroughly until all ingredients are evenly distributed.
03 - Spread 1/2 cup enchilada sauce evenly across the bottom of the prepared baking dish.
04 - Arrange four tortillas over the sauce layer, tearing pieces as necessary to completely cover the bottom of the dish.
05 - Distribute half of the chicken mixture evenly over the tortillas. Sprinkle with 2/3 cup shredded cheese.
06 - Place another layer of four tortillas over the cheese. Top with the remaining chicken mixture and another 2/3 cup shredded cheese.
07 - Arrange the final tortilla layer on top. Pour the remaining 1/2 cup enchilada sauce evenly over the tortillas. Sprinkle with the remaining cheese and black olives if using.
08 - Cover the baking dish tightly with aluminum foil. Bake for 20 minutes.
09 - Remove the foil and continue baking for an additional 10 minutes until the cheese is fully melted, bubbly, and lightly golden on top.
10 - Let the casserole rest for 5 minutes before serving. Top with fresh cilantro, green onions, avocado slices, sour cream, and lime wedges.