Preheat your oven to 180°C (350°F).
Slice off the tops of the bell peppers and carefully remove the seeds and membranes, creating hollow shells.
Heat olive oil in a skillet over medium heat; add chopped onions and minced garlic, cooking until fragrant and translucent, about 3 minutes.
Add ground beef to the skillet, breaking it apart with a spoon, and cook until browned, about 5-7 minutes. Drain excess fat if necessary.
Mix cooked rice, spices (paprika, cumin, salt, and pepper), and tomato sauce into the skillet with the beef mixture. Stir until well combined and heated through.
Spoon the filling mixture into each hollowed pepper, pressing down gently to pack the filling evenly.
Place the stuffed peppers upright in a baking dish. Drizzle a little olive oil over each for extra flavor and moisture.
Bake uncovered in the preheated oven for 25-30 minutes, until the peppers are tender and the filling is bubbling and slightly browned on top.
Remove from oven and let rest for about 5 minutes. The peppers will be hot and the filling set and flavorful.
Serve hot, garnished with fresh herbs if desired, and enjoy the vibrant, hearty flavors of these stuffed peppers.