Preheat your oven to 375°F (190°C).

Carefully slice the tops off the large bell peppers and remove the seeds and membranes inside. Rinse them under cool water.

In a large skillet, heat a tablespoon of olive oil over medium heat and sauté the finely chopped onion and minced garlic for about 3-4 minutes until translucent.

Add the ground beef to the skillet and cook for about 5-7 minutes, stirring occasionally, until fully browned.

Stir in the cooked rice, tomato sauce, drained diced tomatoes, Italian seasoning, and a pinch of salt and pepper into the skillet and simmer for about 5 minutes.

Carefully spoon the beef-and-rice mixture into each bell pepper, packing it gently.

Place the stuffed peppers upright in a baking dish. Trim a small amount off the bottoms to ensure they stand securely.

Pour about 1/4 inch of water into the bottom of the baking dish.

Cover the baking dish tightly with aluminum foil and bake for 35 minutes.

Remove the foil and sprinkle the shredded mozzarella and grated Parmesan cheese on top of each pepper. Bake uncovered for an additional 10-15 minutes.

Once the cheese is beautifully melted, let the stuffed peppers cool for about 10 minutes.

Before serving, sprinkle chopped fresh parsley over the top.