First, soak the raisins in warm water to rehydrate them.
Rub the hake steaks in salt and flour and fry in extra-virgin olive oil until they are lightly golden but not completely cooked. Remove from the heat and strain.
Peel, cut and gently fry the onions in extra-virgin olive oil until they’re translucent. Add ½ spoonful of flour, stir and add the ½ glass of white wine. Add the tomato. Cook over a low heat for about 10 minutes and give it all a whiz in the blender to make a smooth sauce.
Put the hake in a saucepan, cover with the sauce and add ½ glass of water. Add salt, pepper and raisins and cook for 5 minutes.