Preheat oven 175°F.Wash and dry lemons.Zest lemons using a zester, microplane, grater, or peeler. Zest only the yellow rind and avoid zesting the white pith. Spread out the zest in a single layer on a baking sheet. Bake 20-25 or until zest is fully dried.
Transfer to an airtight container. Store at room temperature for up to a year.