01 - Set the oven temperature to 375°F (190°C).
02 - Bring a large pot of salted water to a boil. Blanch the bell peppers for 3 minutes, then drain and place upside down to dry.
03 - Heat olive oil in a skillet over medium heat. Cook onion until softened, about 3 to 4 minutes. Add garlic and sauté for 1 additional minute.
04 - Add ground beef to the skillet, breaking it apart while cooking until browned and fully cooked. Drain excess fat if necessary.
05 - Mix in diced tomatoes, cooked rice, half of the shredded cheese, parsley, oregano, salt, black pepper, paprika, and red pepper flakes. Cook for 2 to 3 minutes until heated through and well combined.
06 - Arrange blanched peppers upright in a baking dish. Fill each pepper evenly with the beef and rice mixture.
07 - Sprinkle remaining shredded cheese over the stuffed peppers.
08 - Pour ¼ cup water into the bottom of the baking dish and cover loosely with aluminum foil.
09 - Bake covered for 30 minutes. Remove foil and continue baking for 10 to 15 minutes until cheese is golden and peppers are tender.
10 - Allow the stuffed peppers to cool slightly before serving.