Peel lemons trying to get only the zest (yellow portion). If you get a little pith (white portion), it is ok, but should not be thick, and the less the better.
Put the zest into a wide mouth sealable jar.
Pour Everclear over the zest and seal the jar.
Place the jar in the freezer and let set for at least two months. Every few days swirl the jar to stir the alcohol.
Once the mixture is a nice deep yellow (around 2-3 months).
Strain the alcohol to remove all lemon peels. Add back into the jar or a sealable bottle.
Add the water and sugar to a small sauce pan over medium-high heat. Stir until all sugar is dissolved. Allow to cool completely.
Add ¼ - ½ cup of the cooled simple syrup to the alcohol. Seal the jar and swirl to mix.
Place jar in freezer and let set for about a week.
Test the limoncello for sweetness. If needed add more simple syrup and repeat the rest time. Continue this process until you have a good sweetness.