How to Make It
Mix the sugar with the candied grapefruit peel. Moisten the outer rim of a martini glass with the grapefruit wedge and coat lightly with the candied-grapefruit sugar.
In a cocktail shaker, muddle the grapefruit pieces. Add ice and the vodka and Cointreau and shake well. Strain into the prepared martini glass and top with the Champagne.