Scrub the new potatoes and cook in boiling salted water until tender. Drain and let cool.

Once cooled, cut the potatoes into bite-sized pieces and place in a large bowl.

Add the kalamata olives, capers, red onion, and flat-leaf parsley to the bowl with the potatoes.

In a small bowl, whisk together the olive oil, red wine vinegar, sumac, Dijon mustard, lemon juice, minced garlic, sea salt, and freshly ground pepper.

Pour the dressing over the potato mixture and toss gently to combine.

Taste and adjust seasoning if necessary. Serve with extra sumac on top.