1 Coat the bottom of your jar with a layer of kosher salt, about 1/4" thick.
2 Rinse and scrub clean the lemons. With each lemon, cut off any stems. Cut off 1/4-inch from the tip of the lemons. Cut the lemons lengthwise in half, but keep the lemon attached at the base, do not cut all the way through. Then make another cut the same way, as if you were cutting the lemons into quarters, but not all the way through.
3 Gently pull open the lemons and sprinkle well with kosher salt, inside and out.
4 Put the prepared lemons in your canning jar and press them down so that their juices come out and rise to the top. Pack the jar with lemons, making sure that they are covered with juice. Add more juice if needed, and add a couple more tablespoons of juice to the top.
5 Close the lid to the jar and let it sit at room temperature on the counter for a few days. Turn the jar upside down a couple times a day, maybe morning and night. After a few days put the jar of lemons in the refrigerator for at least 3 weeks, until the rinds of the lemons soften. Turn the jar upside down every few days while storing in the refrigerator.
6 To use preserved lemons in cooking, remove one from the jar and rinse it to remove the salt. Discard any seeds. Remove the pulp. Thinly slice or chop the preserved lemon rind to use in a recipe.
Preserved lemons can be stored in the refrigerator for up to 6 months.