1. Prepare the zucchini: Preheat your oven to 375°F (190°C). Wash the zucchini and slice them in half lengthwise. Using a spoon or a melon baller, carefully scoop out the insides to create a hollow boat shape, leaving about a ¼ inch of flesh around the skin to hold the structure. Finely chop the scooped-out zucchini flesh and set it aside for the filling.

2. Cook the filling base: Place a large skillet over medium heat and add the olive oil. Add the finely chopped onion and minced garlic. Sauté until soft and fragrant.

3. Brown the meat: Add the ground beef or turkey along with the chopped zucchini flesh to the skillet. Cook until the meat is fully browned and no longer pink, breaking it up into small crumbles as it cooks.

4. Combine the filling: Stir the diced tomato, cooked rice or breadcrumbs, Italian seasoning, salt, and pepper into the skillet. Cook for a few more minutes, allowing the flavors to meld and the excess liquid from the tomatoes and zucchini to evaporate slightly.

5. Stuff the boats: Spoon the hearty meat and vegetable mixture generously into the hollowed-out zucchini boats. Pack the filling down tightly so it mounds slightly above the zucchini skin. Place the stuffed boats snugly into a baking dish.

6. Add cheese and bake: Sprinkle the tops of the stuffed zucchini evenly with the grated Parmesan and shredded mozzarella cheeses. Place the baking dish in the preheated oven and bake for 25 to 30 minutes. The dish is ready when the zucchini skins are tender when pierced with a fork and the cheese is melted and bubbly.

7. Rest and serve: Let them cool for a few minutes before serving to allow the filling to set.