Mix salt and zest in a bowl; work zest into salt with your fingers to release oils and flavor. Spread on a baking tray. Air-dry until dried completely, 8 hours to overnight.
Note: Zest's color will fade over time, but this won't affect taste.
Make ahead: 2 months, kept airtight at room temperature.
Bottle it: 4-oz. jam glass jar, $0.57; specialtybottle.com; BambooImportsMN 3.5-in. oval bamboo spice/salt spoons, $9.8 8/10; amazon.com
Note: Nutritional analysis is per 1/4 tsp.