Sumac is a common spice in Persian and Turkish cooking. In any Middle Eastern cooking, you may see it popping up, actually. It's bright and citrusy, lifting up any dish it's added to. It is the dried and ground fruit of the sumac shrub. It adds a citrus-like tang to dishes. And, it’s not only great in Persian Salad, but also in meat marinades, in salad dressings, in soups, stews or sprinkled on vegetables.  I've ordered it from Amazon in the past, but most recently from Walmart.