Preheat oven to 375°. Slice zucchini in half and slice out the middle to form a "boat." Set zucchini pulp aside for later. Line zucchini boats on baking sheet lined with parchment paper or lightly coated with olive oil.

Heat olive oil in skillet and cook onions until golden. Add garlic and cook for a few more seconds. Add hamburger and cook until no more pink. Add marinara sauce, zucchini pulp, salt, pepper, Italian seasoning. Simmer 8-10minutes.

Spoon mixture into boats and top with cheese. Bake for 15-20minutes until cheese is melted and bubbly.