Wash and dry the lemons.
Peel the lemons, avoiding the white pith.
Place the lemon peels in a large glass jar.
Pour the vodka over the lemon peels.
Seal the jar and store it in a cool, dark place for 7 days.
Prepare a simple syrup by heating water and sugar until dissolved.
Cool the syrup completely.
Strain the lemon-infused vodka into a clean jar.
Mix the strained vodka with the cooled syrup.
Bottle the limoncello and refrigerate before serving.