Found this online while looking up a different cocktail. Another “1920s classic cocktail”, albeit news to me. For all the jazz age classics out there anymore, you’d think the country just walked around half-sauced for a decade (maybe?).
Regardless, pretty standard 2:1:1 pour. Manhattan meets Gibson. The onion is a nice surprise, adds some good salt/pop.
2 oz. rye
1 oz. Fernet
1 oz. Cointreau
Strain and serve into chilled coupe glass. Garnish with a cocktail onion and orange twist.