Black limes are essentially fresh limes that are blanched in salt water (they are briefly scalded in boiling water before being plunged into freezing water) and left to dry until they're rock hard, resulting in golf size, brown to black coloured balls with a brittle texture that easily yields itself to a grinder.
While traditionally sun-dried on banana-leaf mats, black lime can also be made in an oven or dehydrator. Dried limes will probably take around two days to make in the oven, but the result can be stored for up to two years. You know the lime is done if it is light and feels hollow.
Dried limes are also referred to as 'Limu Omani' (they were first made in Oman) and are an essential flavouring ingredient in the cuisines of Iran, Iraq, and other Gulf States. They were originally obtained in this region by leaving the limes to dry on the trees instead of harvesting them.
This simple ingredient has the potential to transform a whole range of dishes with just a small pinch.