01 - Preheat oven to 400°F. Line a baking dish with parchment paper or lightly grease it.
02 - Slice zucchinis in half lengthwise. Scoop out seeds and some flesh, leaving a ½ inch thick shell. Chop scooped flesh and set aside.
03 - Heat olive oil in a large skillet over medium heat. Sauté onion 2–3 minutes until softened. Add garlic, chopped zucchini flesh, and bell pepper; cook an additional 3–4 minutes.
04 - Add ground beef to skillet. Break up with a spoon and cook until browned and cooked through, about 5 minutes.
05 - Stir in diced tomatoes, tomato paste, oregano, basil, paprika, salt, and pepper. Simmer 5–7 minutes until thickened. Remove from heat and stir in chopped parsley.
06 - Arrange zucchini halves in baking dish. Spoon beef and tomato mixture evenly into each boat.
07 - Sprinkle mozzarella and Parmesan cheeses over stuffed zucchinis.
08 - Cover loosely with foil and bake for 20 minutes. Remove foil and bake an additional 5–10 minutes until cheese is bubbly and golden.
09 - Sprinkle extra parsley on top before serving.