Dried barberries
Small dried red berries of the barberry shrub, very tart with a light fruity note.
Barberries are the small, elongated red berries of a thorny shrub, used dried in the cooking of the Caucasus, Iran and Central Asia. They taste sharply sour, almost lemony, with a faint sweetness, and add acidity and colour to rice dishes, meat, fillings and spice blends, usually whole, sometimes ground. Before use they are usually soaked briefly and warmed only very quickly in butter or oil, because their sugar burns fast and turns them bitter. You can find them in Persian, Turkish and Middle Eastern grocery stores, occasionally in health food or organic shops, and by mail order. Good ones are bright red, while dark or brownish berries are old and have lost much of their flavour.
Substitute:
Unsweetened dried cranberries, chopped small and sprinkled with a little lemon juice, come closest, but they are larger, softer and less sharply sour. Sweetened cranberries or raisins make the dish noticeably sweeter and miss the character entirely. In spice blends, where ground barberry provides acidity, sumac can stand in, though it tastes more astringent and less fruity.