- Squeeze the juice from the grapefruit using a citrus press.
- In a shaker, add:
- ice cubes,
- grapefruit juice,
- a few sprigs of rosemary.
- Shake the shaker vigorously for 30 seconds.
- Filter the contents of the shaker into a glass using a cocktail strainer so as not to have any pulp.
- Add the ice cubes.
- Complete with tonic.
- Garnish with a grapefruit wedge and a sprig of rosemary.