Cut the tops off the bell peppers and remove the seeds and membranes. Place them upright in a baking dish.
In a large skillet over medium heat, add a splash of olive oil and sauté the chopped onion until translucent, about 3-4 minutes. Add the minced garlic and cook for another minute until fragrant.
Add the ground beef to the skillet and season with cumin, chili powder, paprika, salt, and pepper. Cook until the beef is browned and fully cooked, about 6-8 minutes.
Stir in the cooked rice and drained diced tomatoes until well combined. Remove the mixture from the heat and taste for seasoning, adjusting as necessary.
Spoon the beef and rice mixture into each prepared bell pepper, packing it in gently.
Top each stuffed pepper with a generous amount of shredded cheese.
Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly, and the peppers are tender.
Once cooked, let them cool slightly before serving.
Notes
Serve garnished with fresh cilantro or parsley and a drizzle of sour cream or avocado crema.