In a cocktail shaker, combine the cranberry juice, vodka, Cointreau, and lime juice. Fill the shaker with ice.
Shake vigorously until the outside of the shake is frosted, about 30 seconds.
Strain into a chilled cocktail glass. Garnish with a strip of orange zest.
Notes
Avoid pure unsweetened cranberry juice. It will make the cocktail tart and astringent. If you only have unsweetened to work with, add a splash of simple syrup to dilute the tart flavor and up the sweetness.
Measure ingredients precisely. Use a jigger or measuring tool to measure each ingredient properly. Precise proportions will make the best-tasting cosmopolitan drink. If you don't have a measuring cup with ounces, 1 tablespoon equals ½ ounce.
Chill the glass. Before you make this recipe, chill a martini glass in the freezer for at least 30 minutes before serving. This is a key step to making a classic cosmopolitan cocktail; it keeps it cold and refreshing!
Shake, don't stir. It really makes a difference with this cosmopolitan recipe! If you don't have a cocktail shaker, you can use a mason jar with a lid to achieve the same effect.