Preheat oven to 375°F (190°C)
Cook 1 cup rice (or use 1 1/2 cups cooked rice)
Brown 1 lb (450 g) ground beef, turkey, or Italian sausage in a skillet with 1 chopped onion and 2–3 minced garlic cloves
Stir in 1–2 tsp Italian seasoning, 1 tsp salt, 1/2 tsp black pepper, and optional red pepper flakes
Mix in 1 can (15 oz/425 g) crushed tomatoes or tomato sauce
Slice tops off 6 large bell peppers; remove seeds and membranes
Parboil peppers 5–7 minutes (or bake uncovered 10 minutes) to soften slightly
Stir cooked rice into the meat mixture
Spoon filling into peppers and pack lightly
Top with 1/2–1 cup shredded mozzarella or cheddar (optional)
Place peppers in a baking dish; add 1/2–1 cup water or sauce to the bottom
Cover with foil and bake 25–35 minutes
Uncover and bake 10–15 minutes more, until peppers are tender and filling is hot
Rest 5 minutes before serving