Peel the cucumber, remove the seeds and cut into small cubes, also cut radishes into small cubes. Whisk the vinegar and oil with salt, pepper and a pinch of sugar. Mix the cucumber and radishes with the dressing, let it steep.
In the meantime, whisk the eggs and cream with the hand blender in a tall vessel. Season with salt and pepper. Heat the butter in a large pan, add the egg mixture. Put the lid on and cover the egg mixture over a mild heat for approx. 8-10 minutes.
Chop the dill and add to the dressing with the shrimp. Taste everything. Spread half of the shrimp salad on the omelette. Fold the omelette and place on a plate. Serve the rest of the crab salad next to it.