Wash the potatoes under cold water and scrub clean. Place in a pot, cover with water, and add salt. Boil, then reduce to a simmer for 15-20 minutes until fork-tender.

In a bowl, whisk together olive oil, lemon juice, sumac, salt, and pepper to create the dressing. Set aside.

Drain the potatoes and let cool slightly. Cut into bite-sized cubes.

In a mixing bowl, combine cubed potatoes with parsley, onion, cucumber, tomatoes, and olives. Top with feta and gently fold together.

Pour the dressing over the salad and toss gently to coat all ingredients.

Taste and adjust seasoning if needed before serving.

Chill in the refrigerator for at least an hour before serving, garnishing with extra parsley.