Heat the oven: Preheat to 375°F (190°C). Lightly grease a 9x13-inch baking dish.
Sauté the aromatics: Warm olive oil in a large skillet over medium heat.
Add onion and cook until translucent, 4–5 minutes. Stir in garlic and cook 30 seconds.
Brown the beef: Add ground beef, salt, and pepper. Cook, breaking it up, until browned and no longer pink, 5–7 minutes.
Drain excess fat if needed.
Season: Stir in chili powder, cumin, smoked paprika, and red pepper flakes. Cook 1 minute to bloom the spices.
Add liquids and rice: Stir in diced tomatoes (with juices), tomato sauce or salsa, broth, rice (uncooked if using broth; cooked if not), beans, and corn. Taste and adjust salt.
Simmer or swap: If using uncooked rice, bring to a simmer for 2–3 minutes to start softening.
If using cooked rice, skip simmering and reduce added broth to 1/4 cup.
Assemble: Transfer the mixture to the baking dish. Smooth the top and sprinkle evenly with cheese.
Bake: Cover with foil and bake 20 minutes. Remove foil and bake another 10–15 minutes, until the cheese is melted and bubbly and rice is tender.
Finish: Let rest 5–10 minutes.
Top with cilantro and serve with lime, sour cream, and green onions.