Prepare the filling:

1. Chop the onion into a medium-dice and finely chop the garlic. Set aside. Slice each zucchini lengthwise. Using a teaspoon or melon baller, carefully hull out the inside flesh from each half taking care to not pierce the outer skin. Place the contents on a cutting board and rough chop. Set aside. Place each cleaned zucchini half into a baking dish large enough to hold all the zucchini halves.
2. In a medium sauté pan over medium heat, add 1 tbsp of olive oil and heat. Add the chopped onion and garlic and a pinch of salt. Sauté until the onion becomes translucent (about 5 minutes). Add the chopped zucchini flesh and continue to sauté until soft (another 5 minutes).
3. Remove the sausage meat from the casing by slitting it open with a knife. Crumble the meat into the pan. Stir into the onion/garlic/zucchini mixture and continue to break it up with a wooden spoon. Cook until no pink remains in the sausage.
4. Add the tomatoes and stir into the mixture breaking up the tomatoes if needed. Cook until the mixture begins to thicken (you don’t want it too soupy). 
5. Turn off the heat and stir in the cooked rice until combined. Season with salt and pepper to taste. Let the mixture cool.

Finish the zucchini:

1. Preheat oven to 350℉.
2. Holding each prepared zucchini half over the cooled mixture, fill the zucchini using your hands or a spoon. Don’t pack it on but create a nice mound of the stuffing in each zucchini. Return the now filled zucchini to the baking dish. Use any remaining filling in eggs for breakfast.
3. Generously sprinkle each zucchini with grated Parmesan cheese. Add 2 tbsp of water to the baking dish to create steam while it cooks.
4. Cover the baking dish with foil (if the foil will touch the tops of the filled zucchini, lightly coat the underside of the foil with oil or cooking spray).
5. Bake the prepared dish for 45 minutes. Remove the foil and bake for another 10 minutes to crisp up the tops.
6. Carefully remove each zucchini to a serving plate and drizzle and accumulated cooking liquid over each zucchini. Serve warm or at room temperature.