Rinse the fish under cold running water and pat dry with paper towel. Lightly coat the fish in the seasoned flour.
Heat the olive oil in a large frying pan over medium–high heat. Add the fish and cook for 2 minutes each side, gently shaking the pan every 10 seconds or so to prevent sticking. Season both sides of the fish with sea salt.
Remove the fish from the pan, place on a baking tray and drizzle with a little extra virgin olive oil.
Discard the oil from the pan and return to high heat. Carefully add the sherry to the pan and stir vigorously to scrape up any cooked-on bits from the bottom of the pan. Mix through the sofrito and salsa romesco and reduce the heat to medium. Add the parsley and fish stock. Cook for 5–10 minutes until a thick sauce has formed. Season to taste.
To serve, spread the sauce evenly around four warmed serving plates using the back of a spoon. Place the fish on top and serve immediately.