Preheat oven to 375°F (190°C). Slice zucchini lengthwise, scoop out centers to create boats, and reserve pulp.
Place zucchini boats in a baking dish, brush with olive oil, season, and bake for 10 minutes.
Cook onion and garlic in olive oil until soft, then add ground beef and cook until browned. Stir in seasonings, zucchini pulp, and marinara; simmer 5–7 minutes.
Fill zucchini boats with beef mixture, top with cheese, and bake for 15–20 minutes until tender and bubbly.
Garnish with fresh herbs before serving.
Notes
For a lower sodium version, reduce salt and use low-sodium marinara.