Cut the eggplant, zucchini, tomato, and onion into bite-sized pieces.
Sauté the onion first in a pan with olive oil.
Add the eggplant, then zucchini, then tomato in order and stir-fry.
Season with salt and pepper.
Cook on low heat until all the vegetables are tender.
Add herbs (basil or thyme) and mix once more.