Tomato–Zucchini Tian

Name: Tomato–Zucchini Tian
Ingredients: 1 medium eggplant, peeled; Salt; 2 medium onions, peeled and chopped; 3 cloves garlic, peeled and minced; 1⁄2 cup extra-virgin olive oil; Freshly ground black pepper; 2 medium zucchini, sliced diagonally; 6 ripe medium tomatoes, sliced; 3-4 sprigs fresh herbs, such as thyme, rosemary, basil or oregano; 1⁄2 cup grated parmigiano-reggiano (optional)