Begin by thoroughly washing the Yukon Gold or red-skinned potatoes. Place them in a large pot and cover with cold water, adding a generous pinch of salt. Bring the water to a rolling boil over high heat, then reduce the temperature and let them simmer for about 15-20 minutes until fork-tender.

While the potatoes are boiling, whisk together extra-virgin olive oil, fresh lemon juice, sumac, salt, and black pepper in a small bowl. Blend until well combined and set it aside.

Carefully drain the cooked potatoes in a colander and let them sit for a few minutes to cool slightly. Once cooled, slice the potatoes into bite-sized cubes.

In a large mixing bowl, add the cubed potatoes, chopped parsley, red onion, cucumber, tomatoes, black olives, and feta cheese. Gently fold these ingredients together.

Drizzle the prepared dressing over the potato and vegetable mixture. Using a large spoon, carefully toss all the ingredients together until they are well coated.

Taste the salad and adjust the seasoning to your preference. Add more lemon juice or salt and black pepper if needed.

Serve the Turkish Potato Salad immediately at room temperature for the best flavor, or chill in the refrigerator for about an hour if you prefer it cold.