01 - Preheat oven to 375°F. Grease a 9x13-inch casserole dish with non-stick spray or butter.
02 - In a large skillet over medium heat, sauté the diced onion and bell pepper for 4–5 minutes until softened. Add minced garlic and cook for an additional minute until fragrant.
03 - In a large mixing bowl, combine the sautéed vegetables, shredded chicken, cooked rice, black beans, corn, ground cumin, chili powder, smoked paprika, salt, and black pepper. Fold in half of the enchilada sauce and half of the sour cream until evenly incorporated.
04 - Spread half of the filling mixture into the prepared casserole dish in an even layer. Sprinkle with half of the cheddar and Monterey Jack cheeses. Layer the remaining filling on top, then drizzle with the remaining enchilada sauce and sour cream. Finish with the rest of the shredded cheeses.
05 - Cover the dish tightly with aluminum foil and bake for 20 minutes. Remove the foil and continue baking for another 15 minutes, or until the cheese is melted, bubbly, and lightly golden on top.
06 - Remove from the oven and let the casserole rest for 10 minutes before slicing. Garnish individual portions with fresh cilantro, sliced jalapeños, diced tomatoes, or a dollop of sour cream as desired.