Sterilize a 1-quart canning jar and lid.
Scrub lemons.
Squeeze 4 lemons and set the juice aside.
Cut 4 lemons in quarters, but not all the way through, leaving the pieces attached at the stem end. Stuff 1 tablespoon on salt into each lemon and press the lemon shut.
Put the lemons in the sterilized jar, pressing them down into the jar. Add the lemon juice, which should just cover the lemons already in the jar. Close the jar.
Leave for 3-4 days. By that time, the lemons should have disgorged some of their juices and their skins should have softened a little. Open the jar, press down the lemons as much as you can, and if needed add fresh lemon juice to cover the lemons entirely.
Close the jar and store in cool place for at least one month. The longer they are left, the better the flavor. (If a piece of lemon in not covered, it may develop a white mold that is harmless and just needs to be washed off.
Before using, scrape pulp of peel. Discard pulp. Rinse peel to get rid of salt.