Lemons are ripening at full tilt hereabouts, bringing a sprightly lift to the dead of winter. An easy way to put this bounty to use is to make the Italian liqueur limoncino. Remove the zest of six lemons, carefully avoiding the bitter white pith of the peel (organic lemons are preferable because they lack the waxy coating of commercial lemons). Put the zest in a clean quart jar or bottle, add 2 1/8 cups of vodka and then cover the jar and let it stand in the sun for 10 days. Make a sugar syrup by boiling two cups of water with 2 1/2 cups of sugar for 10 minutes. Then allow it to cool. Filter the vodka-lemon liquid through cheesecloth or a coffee filter. Then mix in the sugar syrup to taste. Cover and set aside for 10 days. Keep limoncino in the freezer and bring it out when the occasion calls for a cheery after-dinner digestivo.