01 - Preheat your oven to 375°F. Lightly grease a 9x13-inch baking dish.
02 - In a large skillet over medium heat, cook the ground beef until thoroughly browned. Drain off any excess fat.
03 - Add the diced onion, bell pepper, and minced garlic to the skillet with the beef. Cook for 3–4 minutes until the vegetables begin to soften.
04 - Stir in the uncooked rice, black beans, corn, diced tomatoes (including their juices), tomato sauce, beef broth, taco seasoning, cumin, smoked paprika, salt, and black pepper. Mix everything thoroughly to ensure even distribution.
05 - Bring the mixture in the skillet to a gentle simmer. Carefully transfer the entire contents to the prepared baking dish and spread it out evenly.
06 - Cover the baking dish tightly with aluminum foil. Bake in the preheated oven for 35 minutes.
07 - Remove the foil. Evenly sprinkle the shredded cheddar cheese over the top of the casserole. Return the dish to the oven, uncovered, for an additional 10 minutes, or until the cheese is melted and bubbly and the rice is fully cooked and tender.
08 - Allow the casserole to rest for 5–10 minutes before serving. Garnish with sliced green onions and chopped cilantro, if using.