Salad of Potato and Tunny Fish

4 medium potatoes: boiled in their skins. Peel and slice them while still warm, season with salt

and pepper.

1 large onion: slice very thinly.

In a bowl mix the potatoes and onion, add olive oil and a little wine vinegar.

About an hour before serving, mix the tunny fish, in chunks.

Garnish the dish with capers.