Working with 1 lemon at a time, cut the lemons in quarters leaving about a 1/2 to a 1/4 inch intact at the bottom.
Take a Tbsp of sea salt and rub it all over the cut edges.
Now stick it inside the jar and squash it a little. You want the juice to come out and you want to pack the lemons pretty tightly into the jar.
Continue cutting, salting, and squashing until the jar is full, leaving about an inch of head space.
Now take the ones you have left and cut them in half and juice them.
Mix the juice with the sea salt you have left and pour it into the jar to cover everything up.
If there’s not quite enough liquid to cover you can add some water so that everything stays covered.
You may also need to weigh them down to keep them under the brine. I used some glass fermenting weights that I got from Cultures for Health. You could also use a zip lock baggie filled with water. Just make sure that you can get the lid on the jar.
Once your lemons are all safely tucked under the brine, put the lid on the jar. Now put the jar somewhere where it’s not in your way. This ferment will take anywhere from 1 to 4 weeks depending on the size of the lemons and the temperature of your house. Larger ones will take longer, warmer temperatures will speed things up.
Make sure you burp the jar periodically. Gas will build up as they ferment and you don’t want anything shooting out of the top when you open the jar!
The lemons are done when the bubbling has subsided and the rind is soft and pliable.