Mix everything, except for the watermelon, until you get a fine pink cream. Then mix in the watermelon and possibly a few ice cubes. Pass through a hair sieve and refrigerate for at least 1 hour.
Serve in cool plates or bowls with a spoonful of olive oil on top.
As a side dish as you like:
Roasted almond slivers
ground cumin
nice melon cubes.
The ideal light meal for hot days or a simple amuse in small cups, e.g., with a shrimp skewer.