Traditionally,this would get its superb but subtle sourness from dried black limes. We are trying to achieve a similar taste using lemon and sumac – unless you happen to have dried black limes in your possession (try 2-3 or to taste),but for most,this is a more “cupboard staple”-friendly option. It might seem like a considerable amount of sumac,but it’s subtle and lovely with the eggplant and chickpeas.