In a small bowl, combine salt and lime zest. Use your fingers or the back of a spoon to work the zest into the salt, making sure to eliminate any clumps of zest. Store in an airtight container for up to one week, but it will taste best the day it is made.
To jar more for later: Preheat oven to 225ºF. Line a baking sheet with parchment paper. Spread the salt mixture evenly over the parchment-lined baking sheet. Bake for 60 to 70 minutes, until zest has dried. Let cool. If done, the zest should crumble when you rub it between your fingers.
If a fine salt is desired, place the salt into a food processor and pulse until fine. Store in an airtight container or salt grinder up to 3 months.
To rim a cocktail with salt
Pour salt onto a small plate.
Hold a lime wedge in one hand and a glass in the other. Use the lime wedge to moisten the top and outer lip of the glass. A thin layer of fresh lime juice is all you need.
For a traditional rim on the lip of the glass (best for drinks without ice): Hold the glass upside down and lightly place it into the salt. Twist the glass gently to coat the rim. The salt should rest on top of the lip.
For a banded rim on the outer edge of the glass (best for drinks with ice): Roll the lip of the glass in the salt to form an even belt of salt around the outer rim of the glass.
Tap the glass to dislodge any excess.
Notes
The amount of zest you can get varies depending on the size of your limes. On average, a regular lime will make 2 teaspoons of zest. Feel free to substitute grapefruit zest, orange zest or lemon zest in this recipe. See post for other variations. Make sure your glassware is dry before rimming it. Any leftover moisture can pick up extra flacks of salt and sugar.Use freshly cut citrus to moisten the rim of the glass. If no lime, use lemon or orange. The fresh juices help the sugar and salt stick to the rims of the glasses without dissolving right away.Be precise when applying the citrus wedge. Any areas touched by the moisture will get coated in salt and sugar; any areas not coated will be devoid of it.Do your best to keep salt and sugar away from the interior of the cocktail glass. A proper rim should have the grains on the top lip of the glass or a band on the outside of the glass.