Wash the Yukon Gold or red-skinned potatoes under cold running water and scrub them well to remove any dirt. Pat them dry with a kitchen towel.

Place the whole, unpeeled potatoes in a large pot, cover them with cold water, and add a pinch of salt. Bring to a boil, then reduce to simmer and cook for about 15-20 minutes.

Whisk together the extra-virgin olive oil, fresh lemon juice, sumac, salt, and black pepper in a small bowl. Set aside.

Once the potatoes are cooked, drain them and let them cool for 5-10 minutes. Cut into bite-sized cubes.

In a large mixing bowl, combine the cubed potatoes, parsley, red onion, cucumber, tomatoes, and olives.

Pour the dressing over the salad mixture and gently toss until well-coated.

Sprinkle crumbled feta over the salad and let it rest for a few minutes before serving.

Taste and adjust seasoning with extra salt or lemon juice as needed. Serve immediately or chill before serving.