True fact: very few classic cocktails came out of the Prohibition era, but this is one of them. NYC mixologist Karl Franz Williams goes traditional with cognac, orange liqueur, and fresh lemon juice. Then he serves it in a glass with half a sugared rim, so you can have the option of drinking it with or without extra sweetness.
Fill a coupe glass with ice cubes, to chill. Place sugar on a plate. Cut a slit into the center of a lemon wedge (one per cocktail). Set aside.
Add lemon juice, Cointreau, and cognac to cocktail shaker. Set aside. Discard the ice cubes in coupe glass. Run the lemon wedge around half of the glass rim, then gently roll the rim into sugar; the sugar should stick only to the lemon juice on the rim. Set glass aside.
Assembly: Fill cocktail shaker with ice. Cover and shake briefly, about 5 seconds. Strain contents into chilled coupe glass (optional: for an extra smooth cocktail, double strain through a fine-mesh strainer). Garnish with a lemon wedge perched on the rim of the glass. Serve.