If you like a sugared rim, run a lemon slice along the edge of a cocktail glass and dip it into sugar. Put the glass in the fridge to chill.
In a cocktail shaker, combine the brandy or cognac, orange liqueur, and fresh lemon juice. Fill the shaker halfway with ice.
Shake the mixture vigorously until it's chilled, about 20 seconds.
Strain the mixture into your prepared cocktail glass. Garnish with a lemon twist.