Here's a nice lemon twist on a classic Cosmopolitan. The lemon replaces the lime citrus element and becomes an even stronger flavor profile by using a lemon infused vodka.
I like using the Cointreau in place of the Triple Sec because it has a stronger orange flavor which I really like with the cranberry and it has a more complex flavor than the less expensive Triple Sec.
According to the IBA (International Bartender's Association) a classic Cosmopolitan does use a citrus or lemon vodka, but I like that extra citrus kick.
Enjoy!