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 the 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 pepper. Fold in half of the enchilada sauce and half of the sour cream until evenly incorporated.
04 - Spread half of the filling mixture evenly across the bottom of the prepared casserole dish. 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 bubbly and golden on top.
06 - Remove from the oven and let the casserole rest for 10 minutes before slicing. Garnish each portion with fresh cilantro, sliced jalapeños, diced tomatoes, or extra sour cream as desired.