Wash the cucumber and cut into small cubes. Peel and finely dice onions. Wash the lime hot, grate dry and grate the peel thinly. Clean the chilli, cut lengthwise, wash and remove the seeds. Chop the pod finely. Wash the coriander, shake dry and chop the upper third of the stalks finely.
Halve the lime and squeeze the juice of one half. Wash the salmon, dab dry and cut into small cubes. Mix salmon, coriander, lime zest, onions and chilli, season with salt and pepper. Put the salmon tartare in a cool place. Mix cucumbers, olive oil and about 1/2 tsp lime juice and season with salt and a little sugar.
Mix wasabi and sour cream and whisk until thick and creamy. Season cream with salt, pepper and a little lime juice. Cut cress from the bed. Layer tartar, wasabi cream, cucumber cubes and cress in glasses.