Heat 1 TBLS of the oil in a large saucepan and sauté the onions, peppers and garlic until softened and slightly browned, about 5 minutes.
Meanwhile heat a large skillet with the remaining 2 TBLS oil and add the eggplant and zucchini. Saute over medium heat until lightly browned about 7 minutes. Add to the onions.
Add the tomatoes, thyme, bay leaf, salt, pepper, tomato paste and simmer over low heat, stirring occasionally for 20 – 25 minutes. Taste and adjust seasoning.
Add basil and olives and serve with parmesan on top, if desired.