Wash the lemons thoroughly and peel them using a vegetable peeler, avoiding the white pith.

Place the lemon peels in a large glass jar and pour the vodka over them. Seal the jar and let it sit in a cool, dark place for at least 7 days, shaking it gently every couple of days.

In a saucepan, combine the water and sugar. Heat over medium heat, stirring until the sugar is completely dissolved. Allow to cool.

After the infusion period, strain the vodka through a fine mesh strainer into a clean jar, discarding the lemon peels. Add the cooled simple syrup to the infused vodka and mix well.

Transfer the limoncello into a bottle for storage. Refrigerate for at least 24 hours before serving.