Preheat the oven to 375°F (190°C).
Place the bell peppers upright in a baking dish.
Heat olive oil in a large skillet over medium heat.
Add chopped onion and cook for 3-4 minutes until softened.
Add minced garlic and cook for another 1 minute until fragrant.
Add ground beef to the skillet and cook until browned, breaking it apart with a spoon, about 6-8 minutes.
Stir in ground cumin, chili powder, smoked paprika, salt, and black pepper; cook for 1 minute to toast the spices.
Remove the skillet from heat and stir in cooked rice, black beans, and diced tomatoes until well combined.
Spoon the beef mixture evenly into each bell pepper, filling them completely.
Top each stuffed pepper with shredded cheddar cheese.
Cover the baking dish with aluminum foil and bake for 30 minutes.
Remove the foil and bake for an additional 10 minutes, or until the cheese is melted and bubbly.
Remove from oven and let cool for 5 minutes.
Garnish with chopped fresh cilantro and serve with salsa on the side.