1. Slice zucchini in half and use spoon to scoop out the flesh. Set flesh from all zucchini aside.
2. Boil water in a pot and throw in zucchinis for 3 minutes.
3. Remove zucchini from boiling water and set them aside.
4. Chop zucchini flesh you had set aside, and place in mixing bowl. Set aside.
5. Place saucepan with olive oil over medium heat and sauté garlic and onion for 4 minutes, then add chopped zucchini flesh and cook 2 minutes.
6. Remove mixture from heat and set aside.
7. Preheat oven to 350°F.
8. Stuff zucchini halves with sautéed mixture and top with cheese.
9. Place zucchini in baking dish and bake for 15 minutes, until cheese is melted and browned.
10. Boil tomatoes, garlic, and onion for sauce. Once softened, blend tomatoes, onion, garlic, olive oil, salt and pepper.
11. Serve stuffed zucchini with sauce.