Preheat the oven to 375°F (190°C). Cut the tops off the bell peppers and remove the seeds and membranes.

In a skillet over medium heat, cook the ground beef until browned. Add the chopped onion and minced garlic, cooking until the onion is translucent.

Stir in the cooked rice, diced tomatoes, Italian seasoning, salt, and pepper. Mix well and remove from heat.

Fill each bell pepper with the meat and rice mixture, packing it down slightly. Top with shredded cheddar cheese.

Place the stuffed peppers upright in a baking dish. Add a little water to the bottom of the dish to help steam the peppers. Cover with foil and bake for 25 minutes. Remove the foil and bake for an additional 5 minutes until the cheese is bubbly.