To make this Greek Salad, start by making the vinaigrette. In a measuring cup combine rice vinegar, garlic, salt, pepper, sugar, and Za'atar seasoning. While whisking, slowly pour the olive oil into the mixture.
Combine in a bowl, diced onions, halved cherry tomatoes, chopped cucumbers, and feta cheese. Pour the vinaigrette over the salad and toss it gently.
Note: This salad is not one that does well when made ahead, so I recommend making it right before serving.