this simple spritz can be made with either sweet or blanc vermouth (blanc vermouth, less well known in the US, is citrus-driven and less sweet than sweet vermouth, but considerably sweeter than dry vermouth). We top ours with a simple lemon twist, but in Barcelona, the customary garnish is a slice of orange and green olives.
In a small glass, add equal parts chilled vermouth and soda water.
Express the oils from a lemon twist over the top of the glass and enjoy.