Wash and dry the eggplant(s); leave the skin on. Cut eggplant up into small squares. Put the eggplant squares into a colander and sprinkle with salt; leave to drain. Cut the red peppers into small pieces. Chop the onions fairly small and crush the garlic cloves.
Heat olive oil in a 4-quart Dutch oven. Add the onions and garlic and stew until they are pale gold but not brown, about 10 minutes.
Add the eggplant and red peppers. Cover the Dutch oven and let them simmer for 20 to 30 minutes, until tender. Meanwhile chop the tomatoes.
Add the chopped tomatoes and coriander. Stir and taste. Add more salt if necessary, and black pepper. Continue cooking another 5 minutes or so until the tomatoes are tender.