Preheat your oven to 375°F (190°C).
Slice the tops off the bell peppers and carefully remove the seeds and membranes, creating hollow shells for stuffing. Place them upright in a baking dish.
Cook the rice or quinoa according to package instructions until tender, then set aside to cool slightly.
Heat olive oil in a skillet over medium heat. Add chopped onion and cook until translucent and fragrant, about 3-4 minutes. Add minced garlic and cook for another minute, until fragrant.
Add the ground meat to the skillet, breaking it apart with a spoon. Cook until browned and no longer pink, about 6-8 minutes.
Stir in the diced tomatoes, smoked paprika, dried herbs, salt, and pepper. Let the mixture simmer for 5 minutes to meld the flavors.
Combine the cooked grains with the meat mixture in a large bowl. Mix well and stir in shredded cheese for added richness.
Spoon the filling evenly into each hollowed-out pepper, pressing gently to fill completely.
Place the stuffed peppers in the baking dish and cover loosely with foil. Bake for 25 minutes until the peppers start to soften.
Remove the foil and continue baking for another 10-15 minutes until the tops are slightly browned and bubbly.
Once done, remove from the oven and let cool for a few minutes. Garnish with fresh herbs or additional cheese if desired.
Serve hot, and enjoy the vibrant colors and hearty, flavorful filling with a fork and knife.