Sauté onion and garlic 10-15 minutes until softened and browning slightly.
Add eggplant and sauté for another 5 minutes.
Add tomatoes and 3 Tb. water. Cover and continue cooking, adding a bit more water as needed, until eggplant has softened.
Remove from heat and stir in vinegar and olives.
Serve over pasta with parmigiana and walnuts. (Mushroom ravioli work well.)