This deliciously sour fruit is used in Persian and Arab cooking and adds a zestiness to fish, chicken, lamb, lentils, or soups. The flavor is at once astringent and fermented -- in a good way. Add the whole lemons to stews or soups early in cooking. Prick with a paring knife towards the end of cooking and squeeze out the liquid to kick up the tart flavor of your dish. 

Also known as black lime, Persian lime or limu omani.