While this is an incredibly simple dish, it had several faces. When freshly made, the vegetables are crisp and bright. Let it marinate over night, and the vegetables become more like a pickle.
But then you've got another choice... you'll see.
Cool as a Cucumber Salad
1/4 cup wine vinegar (or to taste)
Peel and halve the onions and slice. I like them a little thick, but slice them the way you like them. Put them in a bowl and sprinkle with the salt, and stir to combine.
Peel the cucumbers, cut off the ends, and slice.
At this point, the onions should have exuded some moisture. Rinse them, drain them, and add the sliced cucumbers to the bowl. Add the sugar and vinegar, stir to combine. Let it sit for a few minutes, then taste it to check for the tartness; add more sugar if it needs it. While some salt remains even after you rinse the onions, you can add more if you want it.
Now, here's the twist. After the salad sits overnight, I often turn it into a different salad. I drain all the liquid and add either sour cream or yogurt (preferably Greek-style for the thickness, but regular plain yogurt is fine.) Mix that in, and it becomes a different sort of salad. And while I often leave the first salad un-herbed, I like the creamy version with some fresh dill.