Where I live, “Greek salad” is inevitably served with lots of fancy lettuce, feta cheese (not bad: but most of the time not enough of it), olives (worse: usually the cut-corner, grey-black, pitted, tasteless, guests-eat-anything-whatever-you-give-them kind), a mountain of these unspeakable wedges of raw red onion (that bad) and salad dressing of the customer’s choice (I don’t even say anything). As I experienced salad as served everywhere all over Greece thirty years ago, its bliss came from a seeming lack of sophistication (no lettuce, no elaborate dressing, no fancy decoration) in combination with really fresh ingredients.
You need even quantities of:
Firm specimens of the big, meaty kind of tomatoes.
Green bell peppers, the juicy, crunchy kind, not one of those bitter-tasting wrinkly horrors from the Forgotten Corner.
Good Feta cheese.
Whole Greek black olives. (I observe that the “Kalamata” olive has taken over the world. Considering the fact that Kalamata is just one little town somewhere in the south of the Peloponnese (it rained enormously when I was there, and the food was terrible), this seems suspect. One is reminded of how the whole world buys Beaujolais Nouveau in November, in quantities that would need a country of the size of Brasil to produce. No matter; wherever they come from, the canned Kalamata olives in brine are often fine, but do try your way through the various brands. Use only whole olives.)
Not more than quarter-inch-thick rings of big, sweet, white onions. If the onions you can get are too sharp, soak the rings in cold, salted water for an hour or so.
In my opinion the cucumber must be peeled (I don’t know what kind of anti-bug-stuff they put on them, and also, I don’t like the green skin). Cucumbers and everything else, apart from the onion and the olives, is cubed into nice bite-size bits. All is then distributed evenly on separate dishes and topped with the onion rings. There ought to be salt, a pepper-grinder, white vinegar and grrrrrreen olive oil at the table, so that everyone can experiment with their own dressing.