Pour olive oil in a large pot and heat over high heat. Add onions and garlic and saute for 2 minutes. Lower the heat and add eggplant, zucchini, tomato puree, herbes de Provence, salt, and pepper. Cover and simmer for 30 minutes.
Remove the lid. If there is still a lot of liquid, continue cooking for another 30 minutes uncovered. If the amount of liquid looks right, put back the lid and cook for 30 more minutes.