01 - Preheat oven to 400°F. Line a baking dish with parchment paper or lightly grease it.
02 - Slice zucchini in half lengthwise. Using a spoon, scoop out the seeds and some flesh to create boats, leaving about 1/2 inch shell. Chop the scooped zucchini flesh and set aside.
03 - Heat olive oil in a large skillet over medium heat. Add onion and sauté 2–3 minutes until softened. Add garlic, chopped zucchini flesh, and bell pepper; cook another 3–4 minutes.
04 - Add ground beef to the pan. Cook, breaking up with a spoon, until browned and cooked through, about 5 minutes.
05 - Stir in diced tomatoes, tomato paste, oregano, basil, paprika, salt, and pepper. Simmer for 5–7 minutes until the mixture thickens. Remove from heat and stir in chopped parsley.
06 - Arrange zucchini boats in the prepared baking dish. Spoon beef and tomato mixture evenly into each boat.
07 - Sprinkle with mozzarella and Parmesan cheese.
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 - Garnish with extra parsley before serving.