Add the sugar to a small plate, then rub the lemon zest into the sugar with your fingers until fragrant.
Moisten the rim of your martini glass with a bit of lemon juice or simple syrup. Turn the glass upside down and twist into the lemon sugar and set aside.
Add the vodka, lemon juice, simple syrup, and orange liqueur to a cocktail shaker, then top with ice. Shake vigorously for 30 seconds or until cold. Strain into your sugar rimmed martini glass and enjoy!