Remove the peel from the lemons using a grater, microplane, zester, vegetable peeler, or knife. Be careful not to get any of the white pith. I zest them before cutting and juicing them.
To dry in the oven:
Heat the oven to its lowest heat setting. (My oven’s lowest setting is 170° F.)
Spread the zest on a baking sheet lined with parchment paper. Let it bake until the peel is dry, shriveled, and crispy. If the zest is very fine, it should be finished in 30 minutes to an hour. It will take longer if the peel is in strips, several hours should do it.
To dry on the counter:
Spread the peel on a dish or baking pan and let dry for several days, giving it a toss every day or so. The smaller the peel, the faster it will dry.
To store:
When the peel is completely dry, store it in an airtight container.
The dried peel can be left as is, or ground into a powder in a spice grinder or blender.