Place 1 pound thinly sliced English cucumbers, 1 halved and thinly sliced small red onion in a medium bowl. Sprinkle with 1 ¼ teaspoons kosher salt and toss to combine. Let sit for 20 minutes.
Pour off any liquid from the cucumber mixture. Add 3 tablespoons vinegar of choice and 2 teaspoons granulated sugar, and toss until the sugar is dissolved. Taste and season with black pepper as needed. Add 1 tablespoon coarsely chopped fresh dill if desired and toss to combine.
