Preheat oven to 375F. Slice zucchini in half, and carve them out with a spoon. Chop the zucchini 'meat' and set it aside. Line zucchini boats on a baking sheet lined with parchment paper or lightly greased with oil.
Heat olive oil in a non-stick skillet. Cook onion for 2-3 minutes or until it begins to golden. Ad the garlic and cook for a few seconds. Add meat and cook until it's no longer pink, 3-5 minutes. Add the marinara sauce, zucchini pulp, italian seasoning and salt + pepper. Simmer for 8-10 minutes.
Spoon mixture into zucchini boats and top each with a drizzle of cheese. Bake for 15-20 minutes or until the cheesy is fully melted and bubbly.