There are a few recipes for Dubonnet Royal, but we've opted for an old one which featured in the long out-of-print Café Royal Cocktail Book by W. J. Tarling piblished in 1937.
Add ice to a mixing glass.
Add the first four ingredients to the mixing glass and stir for 20-30 seconds.
Strain into a chilled cocktail glass.
Top with a dash of absinthe and garnish with the maraschino cherry.