Chill a Martini / cocktail glass by putting in cubes of ice and topping up with water while you prepare the ingredients.
Put 50 ml vodka and 25 ml of Cointreau into a cocktail shaker with ice, top up with cranberry juice. Empty the water and ice from the glass, Rub the wedge of lime around the inner and rim. Shake, shake some more, strain and serve immediately. YUM!!