Meyer lemons are especially delicious, but any lemons will work for this recipe. You may substitute two teaspoons superfine sugar for the lemon syrup if desired.
Tint sugar with powdered yellow food color, if desired. Place sugar in a saucer. Moisten the rim of a martini glass with a lemon slice. Dip rim in sugar. In a cocktail shaker, combine vodka, Cointreau, lemon juice, and lemon syrup with ice; shake well. Strain into prepared glass.