01 - Preheat oven to 375°F. Lightly grease a baking dish large enough to hold bell peppers upright.
02 - Heat olive oil in a large skillet over medium heat. Cook chopped onion until softened, about 3 minutes. Add minced garlic and cook for an additional minute.
03 - Add ground beef or turkey to the skillet, breaking it apart with a spatula. Cook until browned and fully cooked, approximately 6 to 8 minutes. Drain excess fat if necessary.
04 - Stir in drained diced tomatoes, tomato paste, cooked rice, oregano, thyme, smoked paprika, salt, and black pepper. Simmer the mixture gently for 5 minutes, then remove from heat.
05 - Mix shredded mozzarella, grated Parmesan, and chopped parsley into the filling. Adjust seasoning as needed.
06 - Arrange hollowed bell peppers upright in the prepared baking dish. Spoon the filling into each pepper, pressing gently to fill completely.
07 - Sprinkle extra shredded mozzarella over the stuffed peppers.
08 - Pour approximately 1/3 cup water into the bottom of the baking dish to generate steam during baking. Cover the dish loosely with foil.
09 - Bake covered for 30 minutes in the preheated oven.
10 - Remove foil and continue baking for an additional 10 to 15 minutes until bell peppers are tender and cheese topping is golden brown. Garnish with extra chopped parsley before serving.