1/4 cup lemon juice (about 1 large lemon)
zest of 1 lemon (thoroughly washed and scrubbed, preferably organic)
1 tbsp Limoncello (optional)
Prepare plain base according to directions, and cool in the refrigerator at least 4 hours, or overnight. When the base is cold enough, add zest, juice and Limoncello (if using) and process in your ice cream maker.
Adapted from The Ciao Bella Book of Gelato and Sorbetto