For many in the midwest, ground black lime sounds pretty exotic. But in Persian cooking, it's a familiar ingredient.
Ground black lime starts with regular green limes. They're picked when ripe, then allowed to dry in the sun until they lose their moisture and they oxidize, turning black all the way through. The super tart fresh lime notes transform into something more savory as they dry. Then the limes are ground into a tangy powder for maximum sprinkle-ability.
These jars of ground black lime come from Guatemala. On the map that's about as far as you can get from Persia, but as it turns out, there's a long history of trade between the two countries: Guatemala exports around 80% of the world's cardamom, a great deal of which winds up in teas brewed in Iran. After many years growing cardamom bound for Iranian tea drinkers, Guatemalan farmer Amilcar Pereira added limes—and ground black lime—to his fields, too. Luckily for us, he keeps some of his crop for sale to the US, too.
This spice is easy to use and brings a sour, bright, citrusy/savory punch to any dish. It's especially great with fish. Toss it into couscous or rice dishes for more depth and fun. Sprinkle it on vegetables. Shake it into cocktails—it's particularly successful in margaritas and sours. Or just use it instead of black pepper for a week and see what you can discover.
"This is sour upon sour, a quick barb of citrus, and then the musk of fermentation beneath."
Ligaya Mishan, The New York Times