One can say that romesco is a development of the Catalan sofregit in which fish (and meat) are normally cooked, but far more and more varied ingredients are used. So in the first recipe you are going to prepare the sauce in which fish of substance are to be cooked after being generously sliced.
The variations of this sauce are legion, secrecy surrounds the method and there is no common agreement among fishermen or cooks about its creation. The annual romescada at Cambrils near Tarragona is in fact a kind of challenge to fishermen to produce the ‘best’ romesco. Four thousand people may turn up to participate in the contest (as onlookers) and a white night is spent by restaurateurs to prepare for the multitude. The master romesco-makers set to work, crouching over their mortars, at little stands in the dazzling April light, engulfed by an excited throng.