Clean the sardines by removing the head and removing the intestines, then open them and remove the bones. Wash them thoroughly under cold running water, pat dry, then lightly dredge in flour and fry them in oil very hot; remove them with a slotted spoon when they are well browned on both sides and place on paper towels to lose the excess of oil. Peel and slice the onions, put them in a pan with a few tablespoons of hot oil and fry them on a medium heat until they begin to brown slightly.
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Pour the vinegar and let it simmer for a few minutes, then remove from heat. Make a layer of sardines in a bowl, not too big, salt lightly and above you have a part of the drained onions, sprinkle with a little ‘hot vinegar, sprinkle with pine nuts and raisins, previously soaked in warm water and wrung out, and continue with these layers.
Finally pour all the remaining vinegar, which will have & agrave; cover for whole fish. Seal the bowl with plastic wrap and marinate sardines in a cool place for at least a day before serving.