If peeled tomatoes are desired, pour boiling water over them and leave for 10 seconds. Drain and peel.
Cut tomatoes into wedges. Peel cucumbers thinly and halve lengthwise. Cut in 1 cm (1/2 inch) slices. Wash, core and seed pepper and remove white membrane. Halve and cut into thick strips. Separate onion slices into rings. Place prepared ingredients in a bowl, & top with the olives. Pour on dressing just before serving.
For dressing: Combine ingredients in a bowl and beat well with a fork or put in a screw top jar, seal and shake well. Beat or shake again just before serving.