1. Preheat the Oven:
- Preheat your oven to 375°F (190°C) and lightly grease a 9×13-inch casserole dish.
2. Cook the Ground Beef:
- Heat a large skillet over medium-high heat.
- Add the ground beef and cook until browned, breaking it into crumbles as it cooks. If needed, add olive oil to prevent sticking.
- Stir in the onion, bell pepper (if using), and garlic. Cook for another 3–4 minutes until softened.
- Season with smoked paprika, oregano, salt, and black pepper.
3. Combine Casserole Ingredients:
- Stir the uncooked rice into the beef mixture.
- Add the beef broth, canned tomatoes (with their juice), and frozen vegetables (if using). Bring the mixture to a gentle boil.
4. Assemble the Casserole:
- Transfer the beef and rice mixture to the prepared casserole dish. Cover tightly with foil to prevent drying out.
- Bake in the preheated oven for 30–35 minutes, or until the rice is tender and the liquid is absorbed.
5. Add the Cheddar Crust:
- In a small bowl, mix the shredded cheddar cheese, panko breadcrumbs, and melted butter.
- Sprinkle the cheese mixture evenly over the casserole.
6. Bake and Serve:
- Return the casserole to the oven, uncovered, and bake for an additional 10–12 minutes, or until the cheese is melted and bubbly and the topping is golden brown.
- Let the casserole cool for 5 minutes before serving.