Boil 2 1/2 cups water and 1 cup sugar, stirring to dissolve the sugar, then remove from the heat and add 2/3 cup lime juice, 1/3 cup tequila, 5 tablespoons triple sec and 1/4 teaspoon salt. Let cool, then stir in 2 teaspoons grated lime zest and pour into a small glass baking dish; cover and freeze for about 4 hours before scraping with a fork. For the full effect, dip the rims of the serving bowls in equal parts sugar and kosher salt, and a pinch of lime zest. Garnish with lime slices.
Photograph by Lisa Shin