How to Make It
Preheat the oven to 350°. Heat 1/4 cup of olive oil in a large skillet. Add the onion and cook over low heat, stirring occasionally, until softened, about 8 minutes. Transfer the onion to a large bowl and let cool to room temperature.
Cut the long zucchini in half lengthwise. Or cut off the top quarters of the round zucchini. Scoop out the insides, leaving 1/4-inch-thick shells.
Add the bread crumbs, parsley and ham to the onion and season with salt, pepper and nutmeg. Mix in the eggs. Season the zucchini shells with salt and pepper and fill them with the stuffing. Cover with the lids if using round zucchini.
Grease a large baking pan with the remaining 1 tablespoon of olive oil. Add the water, garlic and tomatoes and arrange the stuffed zucchini in the pan; drizzle the zucchini generously with olive oil. Cover with foil and bake for 25 minutes. Uncover and bake for 25 minutes, or until browned on top. Spoon the pan juices over the zucchini and serve.