PEEL the cucumbers if their skins are tough or waxed. Trim the stem end of the cucumbers, halve them lengthwise, and scoop out the seeds.
SET the flat side of a half cucumber on a cutting board and cut into ⅛-inch-thick slices. Put the cucumber slices in a large colander.
CUT off the ends of the onion, halve it length-wise, and cut
into thin half-moon slices as well. Add to the colander.
SALT the vegetables generously (about 2 teaspoons), tossing to distribute the salt. Let everything sit for about 40 minutes. This will soften the aggressive flavor of the onion and draw out excess moisture from the cucumber and cure it slightly.
LIFT the cucumbers and onion out of the colander and pile
onto a couple of paper towels. Blot to remove the excess
moisture and salt, then pile into a large bowl.
ADD the vinegar and toss well. Add the yogurt and toss
again. Add the papalo (if using), basil, chives, and dill and
toss again. Season with cracked pepper. Taste and add more salt, vinegar, or pepper to make the flavor pop. Finish with a nice shot of olive oil and toss again.