Wash the lemons thoroughly and use a vegetable peeler to remove the zest, avoiding the white pith.

Place the lemon zest in a glass jar and pour the vodka over it. 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 sugar and water. Heat over medium heat, stirring until the sugar is fully dissolved. Allow to cool.

After the infusion period, strain the vodka mixture through a fine mesh strainer to remove the zest. Mix the infused vodka with the cooled simple syrup. Pour into bottles using a funnel.

Refrigerate the limoncello for at least 24 hours before serving. Serve chilled in small glasses.