This potent, sherry-based cocktail is derived from one described in Jacinto Sanfeliu Brucart's El Bar: Arte y Evolucion del Cocktail (Madrid, 1949). The head bartender at the swanky Palace Hotel in Madrid, Sanfeliu Brucart sweetened his SanRu with Cherry Heering, a cherry-flavored liqueur from Denmark.
1 oz. amontillado sherry
1 oz. Dubonnet Rouge
1 oz. gin, preferably Beefeater
1/2 tsp. Cherry Heering
Pour ingredients into a cocktail shaker filled with 1 cup cracked ice. Cover and shake vigorously for 10–15 seconds. Strain into a chilled cocktail glass. Add a twist of lemon peel and serve.