Preheat your oven to 400°F (200°C).
In a 9×13-inch baking dish, combine onion, bell pepper, uncooked rice, fajita seasoning, and cayenne pepper (if using). Stir evenly.
In a mixing bowl, whisk together chicken broth, green chiles, tomato paste, and olive oil. Pour this liquid mixture into the baking dish, stirring to mix well with the rice.
Add shredded chicken, black beans, and corn kernels to the baking dish. Stir thoroughly until all ingredients are evenly distributed.
Cover the dish tightly with aluminum foil and bake for 65–70 minutes, or until the rice has absorbed nearly all the liquid.
Remove the foil, sprinkle grated cheese evenly across the top, and return the dish to the oven. Bake uncovered for 5–10 minutes, until the cheese is melted and golden.
Let the casserole cool for 5–10 minutes. Garnish with fresh cilantro, green onion, salsa, or avocado (optional). Serve and enjoy!