Cut swordfish into cubes of about 3 cm and marinate them with grated ginger as much as you can (more hours is better).
Chop the onion and sauté it with olive oil and another nice piece of ginger cut small. Season lightly with salt, cover and cook for about 10 minutes. The onion should be transparent.
Turn off the heat, add the marinated fish, cover again and wait about 8 minutes for the fish to be cooked.
Be careful, the fish must be just cooked or else it is sad!
Serve the fish immediately or at room temperature. Do not reheat it because it would be overcooked.
It is most important to use fresh fish. Even if you buy fresh swordfish and freeze it at home, thawing it remains watery and is no longer the same.