01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish.
02 - Heat olive oil in a large skillet over medium heat. Add finely chopped red onion and sauté for 2 to 3 minutes until softened.
03 - Add shredded chicken, black beans, corn, cumin, chili powder, garlic powder, salt, and black pepper to the skillet. Stir and cook for 2 to 3 minutes until heated through. Remove from heat.
04 - Spread ½ cup enchilada sauce evenly on the bottom of the prepared baking dish. Arrange 4 corn tortillas over the sauce, tearing to fit as necessary.
05 - Spread half of the chicken mixture evenly over the tortillas. Drizzle with ½ cup enchilada sauce and sprinkle with 1 cup shredded cheese.
06 - Place remaining 4 tortillas on top, then spread remaining chicken mixture, followed by ½ cup enchilada sauce and 1 cup shredded cheese.
07 - Pour last ½ cup enchilada sauce evenly over the top layer. Cover loosely with aluminum foil.
08 - Bake covered for 20 minutes. Remove foil and bake an additional 10 to 15 minutes until cheese is golden and bubbly.
09 - Allow casserole to rest for 10 minutes before slicing. Garnish with cilantro, sour cream, avocado slices, and lime wedges as desired.