01 - Set the oven to 375°F (190°C) to warm up while preparing ingredients.
02 - Trim tops off bell peppers and remove seeds and membranes. Arrange upright in a baking dish.
03 - Heat olive oil in a large skillet over medium heat. Cook chopped onion until softened, about 4 minutes.
04 - Add minced garlic and cook 1 minute. Incorporate ground beef, breaking apart, and cook until browned through, approximately 6 to 7 minutes.
05 - Mix in diced cherry tomatoes, drained canned tomatoes, cumin, smoked paprika, oregano, salt, and black pepper. Simmer for 5 minutes, allowing liquid to reduce.
06 - Remove skillet from heat and fold in cooked rice, crumbled feta, chopped parsley, and pine nuts if using.
07 - Evenly fill each bell pepper with the beef mixture, gently packing the filling inside.
08 - Replace the pepper tops if desired. Add 2 to 3 tablespoons of water to the baking dish bottom to maintain moisture.
09 - Cover the dish with foil and bake for 30 minutes in the preheated oven.
10 - Remove foil and continue baking for an additional 15 minutes until peppers are tender and tops become lightly browned.
11 - Allow stuffed peppers to cool for 5 minutes before serving. Optionally, garnish with extra parsley.