INSTRUCTIONS
1. 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.
2. 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.