Peel the cucumber and remove the fibrous part of the yellow celery as much as possible. Chop the cucumber and bell pepper coarsely, cut the blanched celery into wedges and cut the onion coarsely.
Put all the vegetables together with the passata in a blender. Taste and season with the vinegar, pepper and salt. Gazpacho should be rather thick but still drinkable. Dilute the soup with a little ice-cold water or add some ice cubes in the glasses.
Pour a little olive oil over the gazpacho and finish with a garnish of your choice: red onion chips, yellow bell pepper cubes, croutons, ...