Preheat oven to 375°F (190°C).
Heat olive oil in a skillet over medium heat.
Add diced onion and cook until softened.
Add ground beef and cook until browned.
Stir in garlic, paprika, cumin, salt, and black pepper.
Mix in cooked rice and half of the tomato sauce.
Spoon the beef and rice mixture into the bell peppers.
Place stuffed peppers in a baking dish and pour remaining tomato sauce over them.
Cover with foil and bake for 25 minutes.
Remove foil, sprinkle cheese on top, and bake another 10 minutes until peppers are tender.