Sumac is a popular spice in the Middle East, which does not get enough attention in the US. Ground sumac is a deep red powder that comes from the red, ripe berries of the sumac bush (related to poison ivy, but definitely not poisonous). It has a very pleasant tart berry flavor, but without the acidity of a fresh lemon. When combined with honey in this recipe, the sumac-spiced chicken has a great balance of sweet and sour.
This recipe comes from the Brown Eyed Baker (http://www.browneyedbaker.com/honey-peanut-butter-cookies/). The honey gives them a richer and deeper flavor that an all-sugar cookie cannot match.