Begin by cleaning the potatoes under cold running water to remove dirt. Cover potatoes with cold water in a large pot, adding salt. Bring to a boil over medium-high heat.

Once boiling, reduce heat to simmer and cook potatoes for 15-20 minutes until fork-tender. Drain and cool slightly.

In a medium bowl, whisk together olive oil, lemon juice, sumac, salt, and pepper. Set aside.

Once cool, chop the potatoes into bite-sized cubes. Transfer to a large mixing bowl.

Gently fold in parsley, red onion, cucumber, tomatoes, black olives, and feta cheese.

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

Taste and adjust seasoning with more lemon juice or salt as needed.

Serve at room temperature or chilled, garnished with parsley.