01 - Preheat oven to 375°F. Lightly grease a 9x13 inch baking dish with cooking spray or a small amount of oil.
02 - In a large mixing bowl, combine shredded chicken, 1 cup enchilada sauce, black beans, corn, diced red onion, cumin, chili powder, garlic powder, salt, and pepper. Mix thoroughly until all ingredients are evenly distributed.
03 - Spread 1/2 cup of enchilada sauce evenly across the bottom of the prepared baking dish.
04 - Arrange four tortillas over the sauce, tearing as necessary to fit and completely cover the bottom of the dish.
05 - Spread half of the chicken mixture evenly over the tortillas. Sprinkle with 2/3 cup of shredded cheese.
06 - Add another layer of four tortillas. Top with the remaining chicken mixture and another 2/3 cup of shredded cheese.
07 - Place the final tortilla layer on top. Pour the remaining 1/2 cup enchilada sauce evenly over the surface. Top 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 uncovered for an additional 10 minutes, or until the cheese is bubbly and lightly golden brown.
10 - Let the casserole rest for 5 minutes before serving. Garnish with fresh cilantro, green onions, avocado slices, sour cream, and lime wedges.