1 tablespoon sugar, for rimming glass
2 ounces vodka
1 ounce elderflower liqueur (like St. Germain™)
1 ounce cranberry juice
Zest 1/2 of the lime into a small bowl and combine with rimming sugar, rubbing the sugar and zest together with your fingers until fragrant. Sprinkle onto a small plate. Cut the lime into wedges, then use one to wet the edge of the serving glass. Gently tap the edge of the glass into the sugar, coating well. Set aside.
Fill a cocktail shaker with ice cubes. Add vodka, elderflower liqueur, cranberry juice, and 1/2 ounce freshly squeezed lime juice. Shake vigorously to combine and strain into the prepared glass. Garnish with a lime wedge and serve.