Combine all liquid ingredients in an ice-filled mixing glass. Stir vigorously for about 15 to 20 seconds. Strain into cocktail glass. Rub the outside of the grapefruit peel (i.e. not the pith side) around the rim of the glass before garnishing drink with it.
2 oz Gin
1⁄4 oz Cynar
1 twst Grapefruit peel (as garnish)
Gin, Sweet vermouth, Cynar, Maraschino Liqueur, Grapefruit peel