Drain the silverskin onions. Cut the cucumbers into slices. Wash the apple, quarter it and cut out the core. Cut the flesh into fine cubes and sprinkle with lemon juice. Mix silver onions, cucumber and apple. Divide trout filet into bite-sized pieces, fold in carefully.
For the sauce, stir mayonnaise, ketchup and orange juice until smooth. Season with salt, pepper and paprika. Spread the sauce on top. Wash the dill, pluck flags from the stems and sprinkle over the salad. Arrange the salad on plates, garnished with lemon and apple slices