1 teaspoon white sugar
2 fluid ounces cognac
1 fluid ounce orange-flavored liqueur (such as Cointreau®)
½ fluid ounce lemon juice
1 cup ice cubes
Sprinkle sugar onto a small plate. Lightly wet half the rim of a chilled martini glass with a damp paper towel. Dip the moistened rim in sugar to coat.
Combine cognac, orange-flavored liqueur, and lemon juice in a cocktail shaker. Add ice, cover, and shake until chilled. Strain into the martini glass.