Preheat oven to 375°F (190°C).

Slice the tops off the bell peppers and remove seeds.

In a skillet over medium heat, sauté onions and garlic until fragrant, about 5 minutes. Add ground turkey and cook until browned.

Stir in diced tomatoes, cooked rice or quinoa, Italian seasoning, salt, pepper, and half of the cheese until warmed through.

Stuff each bell pepper with the filling and place them upright in a baking dish. Pour tomato sauce over each stuffed pepper.

Cover with foil and bake for 30 minutes. Remove foil, sprinkle remaining cheese on top, and bake uncovered for an additional 10 minutes until bubbly.