Make a syrup by combining 1 ½ cups prickly pear fruit (tunas), 3 cups water, and a half cup sugar in a saucepan, bringing it to a simmer, and cooking for about 30 minutes, until thickened. Add juice from half a lime. Strain and chill for an hour. Drizzle over crushed ice with a shot of dark rum or bourbon. Or okay, yeah, tequila.