Wash the potatoes thoroughly under cold running water to remove dirt and debris.

Place the cleaned potatoes in a large pot, cover with fresh water, add a pinch of salt, and bring to a boil.

Simmer the potatoes for 15-20 minutes until fork-tender.

While the potatoes are cooking, whisk together the olive oil, lemon juice, sumac, salt, and black pepper in a mixing bowl.

Once cooked, drain the potatoes, cool briefly, and chop them into bite-sized cubes.

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

Drizzle the dressing over the mixture and gently toss to combine without crushing the potatoes.

Adjust seasoning to taste, adding salt, pepper, or lemon juice as desired.

Chill the salad in the refrigerator for at least 30 minutes before serving.

Serve cold or at room temperature, garnished with additional parsley.