Wash the Yukon Gold or red-skinned potatoes under cold running water to remove any dirt.

Place the cleaned potatoes in a large pot and cover with salted water. Boil for 15 to 20 minutes until fork-tender, then drain and cool.

Whisk together olive oil, lemon juice, sumac, salt, and black pepper in a small bowl to prepare the dressing.

Once cool enough to handle, peel the potatoes if desired, then cut them into bite-sized cubes.

In a large bowl, combine diced potatoes, parsley, red onion, cucumber, tomato, black olives, and feta cheese.

Pour the dressing over the potato mixture and gently toss to combine without mashing the potatoes.

Taste and adjust seasoning as necessary, then allow the salad to rest for about an hour before serving.