Preheat the oven to 300ºF. Combine the lime zest and orange zest on a baking sheet.
Bake 5 minutes. Stir the zest and continue to bake until it is dry to the touch, about 5 minutes more. Remove the baking sheet from the oven and allow the zest to cool completely, about 20 minutes.
In a medium bowl, combine the salt and sugar. Add the zests and stir until evenly distributed. Divide the salt mixture between 2 (4-ounce) jars with tight-fitting lids. Store in a cool, dry place for up to 6 months.
Recipe reprinted with permission from <a href="http://www.amazon.com/gp/product/0762444886/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0762444886&linkCode=as2&tag=craftfocom-20&linkId=3FOPK23ECBYVEAU6">"Edible DIY: Simple, Giftable Recipes to Savor and Share"</a> © 2012 by Lucy Baker, Running Press, a member of the Perseus Books Group.