1. In a jar with tight-fitting lid, put together all dressing ingredients and shake well.
2. Core tomatoes and cut them into thin slices.
3. Lengthwise cut avocadoes in half, remove pit, peel and slice lengthwise.
4. In a large, shallow glass dish, arrange slices of tomato and avocado; shake the jar of dressing of pour enough dressing over the slices to cover them completely.
5. Cover the dish and refrigerate for about 2 hours.
6. Drain slightly and serve over salad greens.