This salad lends itself well to improvisation. Try adding some sliced imported olives, capers, chopped sweet peppers, or yellow or orange tomatoes. If making it ahead, wait to add the lettuce and tomato until just before serving time.
Hold one quarter of a head of iceberg lettuce firmly against a cutting board. Using a sharp knife, slice the lettuce thinly. The slices willl separate into long, thin shreds.
Peel the onion and cut in half lengthwise from top to root end. Place on a cutting board, cut-side down. Hold firmly and cut crosswise into 1-inch-thick slices. The slices will separate into half circles and then in pieces.