Combine sugar and lime zest. Use your fingers to rub the sugar into the zest.
Store in a food-safe, airtight container.
To jar more for later: Preheat oven to 225ºF. Line a baking sheet with parchment paper. Spread the sugar 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.
To rim a glass: Place margarita sugar on a plate. Rub a lime wedge around the edge of the glass. Roll the rim of the glasses in the sugar to coat the rim.
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.