4 cups boiling water
1 cup (about 7 ounces) sugar
1 cup fresh juice and 1 tablespoon zest from about 8 lemons
2 teaspoons lemon extract
In a large bowl or measuring cup, dissolve sugar in boiling water. Whisk in lemon juice, lemon zest, and lemon extract. Cover and chill completely, 2 to 3 hours.
Add mixture to electric ice cream maker and prepare according to manufacturer’s directions until icy crystals form and you have a thick, slushlike mixture. Transfer to a large bowl or container and return to freezer to freeze to desired degree of firmness, about 2 to 3 hours.