Soak the red onion in a bowl of heavily salted ice water, 15 minutes.
Meanwhile, whisk the vinegar, lemon zest and juice, honey, dried oregano, 1/2 teaspoon salt and 1/4 teaspoon pepper in a large bowl. Whisk in the olive oil in a slow, steady stream until emulsified. Add the tomatoes and olives and toss. Peel the cucumbers, leaving alternating strips of green peel. Trim the ends, halve lengthwise and slice crosswise, about 1/2 inch thick; add to the bowl with the tomatoes. Drain the red onion, add to the bowl and toss. Drain the feta and slice horizontally into 4 even rectangles. Divide the salad among plates. Top with the feta and oregano; drizzle with olive oil and season with pepper. Photograph by Johnny Miller