Preheat your oven to 375°F (190°C).Cook the chicken and vegetables: In a large skillet, heat the olive oil over medium-high heat. Add the chicken, bell peppers, and onion. Season with chili powder, cumin, garlic powder, paprika, salt, and pepper. Cook until the chicken is browned and the vegetables are tender.Combine: In a large bowl, mix the cooked chicken and vegetables with the cooked rice, black beans, corn, and salsa.Assemble the casserole: Transfer the mixture to a greased 9x13 inch baking dish. Sprinkle the shredded cheddar cheese evenly over the top.Bake: Bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly.Garnish and serve: Garnish with fresh cilantro. Serve hot with a dollop of sour cream on top.