Preheat your oven to 375°F (190°C).
In a skillet, brown the ground beef over medium heat until fully cooked; drain excess fat.
Add chopped onion and minced garlic to the skillet; sauté until soft.
Stir in cooked rice, diced tomatoes, Italian seasoning, salt, and pepper.
Mix thoroughly and remove from heat.
In a baking dish, arrange the halved bell peppers cut side up.
Fill each pepper half with the meat and rice mixture.
Pour tomato sauce over the stuffed peppers.
Cover the dish with aluminum foil and bake for 30 minutes.
Remove foil, sprinkle cheese on top, and bake uncovered for an additional 15 minutes until cheese is bubbly.