Preheat the oven to 375°F and lightly grease a 9x13-inch baking dish.

Slice the tops off the bell peppers and remove the seeds and membranes. If needed, trim a very thin slice from the bottoms so they stand upright without cutting through.

Heat the olive oil in a large skillet over medium heat. Add the ground beef and chopped onion and cook for 6 to 8 minutes, breaking up the meat, until the beef is browned and the onion is softened. Drain excess grease if needed.

Stir in the minced garlic and cook for 30 seconds until fragrant.

Add the drained diced tomatoes, tomato paste, Italian seasoning, kosher salt, and black pepper. Stir well to combine.

Add the cooked rice and 1/2 cup of the shredded cheese. Stir until the filling is evenly mixed and heated through. Taste and adjust seasoning if needed.

Spoon the filling evenly into the prepared peppers and arrange them upright in the baking dish. Pour the water or broth into the bottom of the dish around the peppers.

Cover the dish loosely with foil and bake for 30 minutes.

Remove the foil, sprinkle the remaining 1/2 cup cheese over the tops, and bake uncovered for 10 to 15 minutes more, until the peppers are tender and the cheese is melted and lightly golden.

Let the stuffed peppers rest for 5 minutes before serving. Garnish with chopped parsley and spoon some cooking juices over the top if desired.