Heat a large, deep skillet or Dutch oven over medium-high heat. Add the ground beef and diced onion, then cook while breaking the beef into small pieces until the meat is browned and the onion begins to soften. Drain excess fat if necessary.

Add the minced garlic and cook for about 30 seconds, stirring constantly. The garlic should become fragrant without browning.

Stir in the diced bell peppers, undrained diced tomatoes, tomato sauce, beef broth, uncooked rice, Italian seasoning, Worcestershire sauce, paprika, salt, and black pepper. Mix well so the rice is distributed through the liquid.

Bring the mixture to a boil, then reduce the heat to low. Cover the skillet and simmer for approximately 20 to 25 minutes, stirring once or twice, until the rice is tender and most of the liquid has been absorbed.

Remove the skillet from the heat and let the casserole stand covered for 5 minutes. This resting time allows the rice to absorb remaining sauce and helps the texture set.

Sprinkle the shredded cheddar or mozzarella evenly over the casserole. Cover for another 1 to 2 minutes, or place the skillet briefly under the broiler, until the cheese is melted and bubbly.