Using a sharp hand peeler, remove the rind from the lemons, peeling off as little of the white pith as possible. (Don’t worry, alittle won’t matter much.)
Place the peel in a clean 2-cup jar that has a tight-fitting lid, packing lightly. Pour the grain alcohol over the peel to cover completely, filling the jar to the top. Cover tightly. Label and date the jar. Set on the counter in a place where you’ll remember to shake it at least a few times a day. (I leave mine by the sink.) Give the jar a shake, turning it upside down, at least twice a day, for 2 weeks or longer. I’ve left a batch macerating (steeping) for up to 2 months—the longer you leave it, the stronger the lemon flavor, but 2 weeks will produce a good flavor, too. As the days pass, you’ll notice that the color of the alcohol changes from clear to a cloudy pale yellow color. Be patient. After 2 weeks to 2 months, the lemons will have flavored the alcohol and you can proceed with the recipe.
Measure the granulated sugar and the water into a small pot and set it over a high heat. Bring it to a boil, stirring occasionally until the sugar is dissolved. Remove the pot of sugar-water (the mixture is called simple syrup) from the stove and set it on a trivet on the counter to cool to room temperature. When cool, set a strainer over a medium-sized bowl. Pour the contents of the jar (the lemon peel and alcohol) into the strainer so that the alcohol drains into the bowl and the peel stays in the strainer. Pour the simple syrup over the peel and allow it to sit, draining, for a few minutes. Using the back of a wooden spoon, press out as much alcohol and simple syrup as you can. You now have limoncello. You can discard the peels or you can candy them—but remember, they’re not for kids!
Using a whisk, beat the limoncello to completely combine. Taste it for sweetness. It’s always as I like it, but if you prefer a sweeter version, you can always make alittle more simple syrup, cool it, and add it to the limoncello. Pour your limoncello into clean jars or bottles. Label and date the jars. It’s ready right now, but if you can wait a couple of weeks, the flavors will meld nicely. Store your limoncello in the freezer because it’s best when it’s icy cold.