Black lemons are actually dried limes and owe their misnomer to English translation from Arabic. They're used in the Middle East and surrounding regions as a souring agent in chutneys, soups, and stews, and even ground into flatbreads. They are made by boiling ripe limes in salt water, and then sun drying until the insides turn black.
The powder made from black lemons has a sweet-tart flavor that is unique and has no substitute. Black limes are usually used in legumes, seafood, or meat dishes. They are pierced, peeled, or crushed before adding them to the dish. After cooking they become softer and edible. They can also be powdered and added to rice dishes.
Black limes are strongly flavored. They taste sour and citrusy like lime but they lack the sweetness of fresh limes. Because they are preserved they also have a slightly bitter, fermented flavor.