Sumac is a Middle Eastern Spice made from ground up dried berries. Widely used across the world, sumac is renowned for its bright burgundy colour as well as tart citrusy flavour. Whilst it can be used in dry rubs, or as a seasoning in casseroles and soups, it is most frequently used sprinkled on top of the various dishes. In this recipe, we use it to enhance the flavour of lemon in the tahini dressing. But if you can't get hold of any sumac, substitute it with zaatar, amchoor or lemon pepper, or skip it altogether.