Summer Americano

Chill a highball glass to prepare it for serving.

Slice a lemon into a wheel to use as a garnish.

Combine the sweet vermouth, Italian red bitter liqueur, gentian liqueur, and cardamom bitters in a mixing glass with ice. Stir the mixture until well-chilled.

Strain the mixture into the ice-filled highball glass while simultaneously pouring in the tonic water.

Garnish the cocktail with the prepared lemon slice.