Preheat the oven to 350°F (175°C).
Cut the tops off the bell peppers and remove seeds and membranes. Boil the peppers in a large pot of water for 5 minutes to soften slightly. Drain and place upside down on paper towels.
In a large skillet over medium-high heat, cook the ground beef and chopped onion until beef is browned. Add garlic and cook for 1 more minute.
Stir in cooked rice, most of the tomato sauce (reserve a few tablespoons for topping), Italian seasoning, salt, and pepper. Cook for a few minutes until heated through.
Fill each bell pepper with the beef and rice mixture. Place upright in a baking dish. Top each with a spoonful of the reserved tomato sauce and a generous sprinkle of shredded cheese.
Cover the dish with foil and bake for 30 minutes. Remove foil and bake another 10–15 minutes, until the cheese is melted and bubbly.
Serve hot and enjoy!