Cut the ends off lemons. Placing lemons vertically on their ends, cut in quarters but not all the way through. Spread lemons open and cover with sea salt, inside and out (you can also use kosher salt). Place lemons in fruit jar, packing them down and adding more salt.
Seal the jar and let sit at room temperature for a couple days. Turn the jar upside down occasionally. Put in refrigerator and let sit, again turning upside down occasionally, for 4 weeks, until lemon rinds soften.
To use, remove a lemon from the jar and rinse thoroughly in water to remove salt.
You can store preserved lemons in your refrigerator for up to 6 months.