Fill a cocktail shaker with ice.
Add vodka citron, triple sec, fresh lime juice, and cranberry juice.
Shake vigorously for 10–12 seconds until well chilled.
Double-strain into a chilled cocktail glass.
Garnish with a flamed or expressed orange twist.
Though often associated with 1990s pop culture, the Cosmopolitan was refined by bartender Toby Cecchini in New York around 1988 - use Cointreau over generic triple sec and always opt for freshly squeezed lime juice for the brightest, most balanced result.
My Bar Shelf reads your shelf and shows you every cocktail you can make from what you already own, including Cosmopolitan.