Preheat your oven to 375°F (190°C).

Wash the bell peppers thoroughly. Cut the tops off and remove the seeds carefully.

In a large skillet over medium heat, add the ground beef or turkey and chopped onion. Cook until the meat is browned and the onions are softening, approximately 5–7 minutes. Drain any excess fat.

Add the cooked rice, diced tomatoes, garlic powder, Italian seasoning, salt, and pepper to the skillet. Stir to combine well, cooking for another 2–3 minutes just to warm everything through.

Spoon generous amounts of the meat and rice mixture into each bell pepper, packing it down as you go. Top each of them with a sprinkle of shredded cheese.

Arrange the stuffed peppers upright in a baking dish. If desired, add a little water to the bottom of the dish to keep them moist during baking. Cover with foil and bake for 25 minutes. Remove the foil and bake for an additional 10 minutes until the cheese is melted and bubbly.

Allow the stuffed peppers to cool slightly before serving. Garnish with fresh herbs if desired.