To make it, you'll need only lemon peels, high-proof alcohol, sugar, and water. Simply peel your lemons and combine the peels in a jar with a high-proof vodka or grain alcohol.
Store this jar in a dark place until the lemon peels have dulled. After that, strain the peels from the infused alcohol and add some simple syrup made from sugar and water.
Now, you can add the limoncello to some vibrant summer cocktails, such as a French 75, Hugo, or Aperol. It can enhance just about any citrus-based cocktail.