Quarter cucumber lengthwise and slice, then chop tomatoes, onion, and parsley.
Add the chopped vegetables and parsley to a large bowl and toss gently to combine.
In a small bowl, whisk together the lemon juice, olive oil, dried mint, sumac, salt, and black pepper.
Right before serving, drizzle the dressing over the salad and toss gently. Serve right away.
Notes
Add the dressing right before serving. The salt draws water out of the cucumbers and tomatoes, which can make it soggy, especially if it sits too long.
Cut the cucumbers, tomatoes, and onions into similar-sized pieces so you get a little of everything in each bite.
It's best to eat Arab salad the same day you make it. It doesn't store well.
This salad is wonderful scooped up with fresh Middle Eastern pita bread, which makes it easy to enjoy every last bit of that lemony dressing.
Feeling fancy? Toss some feta cheese into your Arabic salad!