How to Make It
Using a paring knife, working away from you, carefully scrape off any cactus thorns. Cut off the ends of the fruit and, using the tip of the knife, score the fruit lengthwise. Slip you thumb under the skin and peel the fruit. Discard the peel and thorns, then dice the fruit.
In a blender, combine the prickly pear, lime juice, water, agave and salt; puree until smooth. Pour through a fine wire-mesh strainer; discard solids. Pour liquid into . Freeze until firm, at least 4 hours.