01 - Preheat oven to 375°F. Lightly grease a 9x13 inch baking dish with cooking spray or a thin layer 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 to prevent sticking.
04 - Arrange four tortillas over the sauce, overlapping as needed and tearing pieces to fit corners for complete coverage.
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 remaining chicken mixture and another 2/3 cup shredded cheese.
07 - Place the final tortilla layer over the top. Pour remaining 1/2 cup enchilada sauce evenly across the surface. Top with remaining cheese and black olives if desired.
08 - Cover the baking dish tightly with aluminum foil. Bake for 20 minutes to heat through and meld flavors.
09 - Remove foil and bake for an additional 10 minutes until cheese is bubbly and begins to turn golden brown.
10 - Let the casserole rest for 5 minutes before cutting. Garnish with fresh cilantro, green onions, and avocado slices. Serve with sour cream and lime wedges on the side.