Dice eggplant, discarding ends.
In a large frying pan, heat oil over medium-high heat; add eggplant, tomato sauce, garlic, green pepper, cumin, cayenne, sugar, salt, and vinegar.
Cook, covered, over medium heat for 20 minutes.
Uncover and boil mixture over high heat, stirring, until reduced to about 3 cups.
Cover and chill at least 2 hours or until next day.
Before serving, stir in coriander.