Cut cucumber into slices, approximatly 2-3mm thick. Using a mandolin makes this easy
Season the cucumber with salt, and place in a bowl while you make your dressing
Combine sour cream, kewpie mayo and fresh dill. You can add a squeeze of fresh lemon juice as well at this point.
Now, once you have made the dressing, some liquid should have drained out of the cucumber slices. Drain this out of the bowl and discard.
Combine cucumber and dressing. That's it.