In a large bowl, combine the zest, cilantro, and salt.

Line a rimmed baking sheet with parchment paper and spread the salt combination out in an even layer.

Place the baking sheet in a place where it won't be bumped and let it air dry for 4 to 7 days, until completely dry.

Transfer the salt to a jar. This salt keeps its flavor for about six months. After that point, the flavors begin to fade.