Sift the flour over a basin and add baker's yeast broken down in some water with dissolved salt. Mix it all in order to have consistent dough. Then add the softened butter and knead it little by little. The dough will be ready when it no longer sticks to your hands or the basin.
Sprinkle some flour, cover it with a cloth, and involve it in a blanket. Leave it to rise in the warm shade until the dough doubles in size.
In the meantime, chop the onions and sauté the chopped onions with olive oil and soaked, shredded, skin and boneless codfish fillets. Let it boil until the codfish is soft. After the dough has risen, remove about 2/3 and roll it out on a tray that has been greased with olive oil. In order to roll out the dough dip your hands in olive oil and roll it out until it covers the bottom and sides of the tray.
Place the codfish mixture on top and cover it with the remaining dough also rolled out. Afterwards, pull the dough from the sides of the tray towards the top and join the ends together so that the filling does not fall out. Grease the surface of the loaf with olive oil and place it in a hot oven.
Please Note: This loaf should be flat.