You will need to start the preparation for this dish well in advance. Seal the octopus in a plastic bag and leave it in the freezer for two weeks (this helps to tenderize it). Then transfer it to the fridge the day before you want to cook it to allow it to thaw gently for 24 hours.
The next day, clean the octopus by turning the body inside out and pulling away the entrails and bone-like strips sticking to the sides. Locate the stomach sac, which is about the size of an avocado stone, and cut it away.
Wash the octopus well inside and out and then turn the body right side out again. Press the beak and the soft surround out from the centre of the tentacles, cut out and discard.
Simmer the octopus for at least 1 hour in plenty of water to which you have added the onion and bay leaves. Test after half an hour and cook for a further 30 minutes if it is still a bit tough. Do not cook any longer than that, though, as it looses its fresh taste with long cooking.
Lift the octopus out of the pan and drain away all the excess water. Put it on a board, cut off the tentacles and thinly slice each one on the diagonal.
Cut the body into similar-sized pieces, place them on 4 small pine boards or on one large warmed serving plate and sprinkle with the paprika and the cayenne.
Heat the olive oil in a small pan until it is sizzling. Drizzle it over the octopus and then finally sprinkle with the sea salt. Serve with plenty of crusty fresh bread.