Make sure to dry the fish completely. Use paper towels and dab it well.
In a processor add all the ingredients mentioned above EXCEPT the fish.
PULSE it a few of times. Do not blend continuously. We want the walnuts to still have their crunch. You should end up with a chunky marinade.
Transfer the mixture to a bowl and taste to adjust the salt if needed.
Coat the fish on both sides and leave it for 15- 20 minutes in the refigerator.