01 - Preheat your oven to 375°F. Lightly grease a 9x13 inch baking dish with cooking spray or a thin layer of oil.
02 - In a large bowl, combine shredded chicken, 1 cup enchilada sauce, black beans, corn, 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 to prevent tortillas from sticking.
04 - Layer four tortillas over the sauce, tearing as needed to fit and completely cover the bottom of the dish.
05 - Spread half the chicken mixture evenly over the tortillas. Sprinkle with 2/3 cup shredded cheese to create a cohesive layer.
06 - Add another layer of tortillas, then top with the remaining chicken mixture and another 2/3 cup of cheese, pressing gently to compact.
07 - Place the final layer of tortillas over the top. Pour the remaining 1/2 cup enchilada sauce evenly over the surface. Top with the remaining cheese and sliced black olives if using.
08 - Cover the dish tightly with aluminum foil and bake for 20 minutes to allow flavors to meld and tortillas to soften.
09 - Remove the foil and bake uncovered for an additional 10 minutes, or until the cheese is bubbly and golden brown.
10 - Let the casserole rest for 5 minutes before cutting. Garnish with cilantro, green onions, and avocado. Serve with sour cream and lime wedges on the side.