In a large skillet, brown the ground beef and chopped onion over medium-high heat. Drain off any excess grease.
Stir in the garlic powder, salt, and pepper.
Add the diced tomatoes (with their juice), uncooked rice, and beef broth to the skillet. Stir to combine.
Bring the mixture to a boil, then reduce heat to low, cover, and simmer for 20-25 minutes, or until the rice is cooked and liquid is absorbed. Stir occasionally.
Stir in the shredded cheddar cheese until melted and combined.
Serve hot.
Notes
This casserole is great on its own or served with a side salad.