These preserved lemons last for 6 months. The flavor is potent, so use no more than a wedge per 4 servings at first; you can always add more to your taste.
Wash and dry a glass jar with a tight-fitting lid. Set a bowl and a ⅓-cup measure on the counter where you will be working. Wash and dry the lemons. Hold a lemon upright. Using a sharp knife, carefully cut the lemon in half, but not all the way through. Cut about three-fourths o