01 - Preheat the oven to 400°F.
02 - Cut zucchini in half lengthwise and scoop out the flesh with a spoon, leaving a half-inch shell. Chop the reserved flesh.
03 - Arrange zucchini halves cut-side up in a baking dish. Drizzle with 1 tablespoon olive oil and season lightly with salt and pepper.
04 - Heat remaining 1 tablespoon olive oil in a skillet over medium heat. Sauté onion until soft, about 3 minutes. Add garlic and cook for 30 seconds.
05 - Add ground beef to the skillet and cook, breaking up the meat, until browned, approximately 5 to 6 minutes. Drain excess fat if needed.
06 - Stir in chopped zucchini flesh, diced tomato, tomato paste, oregano, basil, paprika, salt, and pepper. Cook for 5 minutes, until vegetables soften and mixture thickens.
07 - Spoon the beef mixture evenly into zucchini shells and top with shredded mozzarella cheese.
08 - Cover the baking dish with foil and bake for 20 minutes.
09 - Remove foil and bake 5 to 10 minutes longer, until cheese is golden and bubbly.
10 - Sprinkle with chopped fresh parsley before serving, if desired.