Wash and dry the lemons. Then zest them using a microplane or peel them using a vegetable peeler or knife. But do not include any of the bitter white pith under the peel.
Put the zest from all the lemons in a sterilized glass jar and then pour in the grain alcohol. There should be enough alcohol to completely cover all the lemon peels.
Put the lid on the glass jar and seal it tightly. Now, store it in a cool dark place for at least 4 days and up to 20 days. The longer the peels are left in the alcohol the more your limoncello will taste of lemon.
Heat the sugar and water together in a small saucepan over medium heat until the sugar has completely dissolved. Then let the simple syrup cool to room temperature.
Strain the alcohol and discard the lemon peels. The liquid should be dark yellow in color and have a strong lemon smell.
Pour the cooled simple syrup into the strained alcohol and mix well. Then pour the mixture into bottles and seal them tightly. Now, let the bottles sit in a dark place for at least 2 days and up to 10 days. The longer you wait the more intense the lemon flavor.
Notes
If your limoncello is too strong for your tastes, try adding a cup of water at a time until it’s diluted to a level you’re comfortable with.