These are an important item in the cuisines of Persia (Iran) and
countries that have been under Persian influence. Limes are boiled in
salt water, then sun dried. Used in lentil, rice or meat dishes they
may be crushed or may simply be pierced and added whole to slow
simmering dishes to provide tartness and a citrus fragrance. The hard
outer shell contains mainly a dry black powder. Size may vary, and
color may vary from tan to black.
More on Citrus.
These limes are essential to the cuinsines of Persia, the Middle East and Levant. They can be simply pierced and added to long cooking soups or stews, then squeezed out and discarded, or for other uses, especially rubs on meats or short cooked recipes, they can be ground to powder. Powdered, they are now being used as a mixed drink ingredient at fancy bars.
Use the light colored ones for light colored dishes, and the black ones for darker dishes.