Make limoncello by infusing vodka with lemon zest in a jar before adding sugar syrup, filtering the mixture into bottles and allowing the liqueur to mature. The entire process takes approximately three weeks.
To make limoncello according to the recipe on LeitesCulinaria.com, peel the yellow zest from 8 lemons while avoiding the bitter white pith, then place the zest in a quart jar. Fill the jar up to about three quarters with strong vodka. Cover tightly with a lid and place it in a cool, dark location in the house. After one week, simmer 2 cups granulated sugar in 4 cups of water in a large saucepan until the sugar dissolves and the liquid is clear. Allow the sugar syrup to cool thoroughly.
Remove the zest from the vodka, then stir the lemon-infused vodka into the sugar syrup. Sieve the mixture and transfer it into bottles. Place the bottles in a cool, dark location for another 15 days, then keep them in the refrigerator or freezer.
The creamy limoncello recipe on Epicurious.com has a similar approach, but uses milk instead of water to create the sugar syrup. It also omits the maturation step. Meanwhile, the rosemary limoncello recipe on MyRecipes.com includes a sprig of rosemary in addition to the lemon zest during the infusion process.