This soup calls for truly ripe tomatoes, the kind that are sweet and fragrant and not ripe in appearance only. Those wrinkled tomatoes that are left on the vine to ripen at the very end of the summer would be the best. The sugars are concentrated, and they give the soup sweetness, body, and density of flavor. In contrast, the mild, tart edge of the green peppers is just right. This green pepper soup is even better the second day.