Preheat the oven to 375°F (190°C).
Prepare the bell peppers by cutting off the tops and removing the seeds and membranes. Set aside.
Heat 1 tablespoon of olive oil in a large skillet over medium heat.
Add the chopped onion and sauté for 3-4 minutes until translucent.
Add the minced garlic and cook for another 1 minute until fragrant.
Add the ground beef to the skillet. Cook, breaking it apart with a spoon, until browned and cooked through, about 6-8 minutes.
Add the diced zucchini and carrot to the skillet. Cook for 4-5 minutes until slightly softened.
Stir in the diced tomatoes, tomato paste, dried oregano, dried basil, smoked paprika, sea salt, and black pepper. Mix well and cook for another 5 minutes, allowing flavors to combine and excess moisture to reduce.
Remove the skillet from heat and stir in the chopped fresh parsley.
Drizzle the remaining 1 tablespoon of olive oil inside the hollowed bell peppers.
Stuff each bell pepper with the beef and vegetable mixture, pressing down gently to fill completely.
Place the stuffed peppers upright in a baking dish.
Cover the baking dish with aluminum foil and bake in the preheated oven for 30 minutes.
Remove the foil and bake for an additional 10 minutes to lightly brown the tops.
Remove from the oven and let cool for 5 minutes before serving.