Fillets of sea bass, sole or turbot prepared in this way are equally good. It is important that the fillets are roughly the same shape, size and thickness.
Grate the zest from the oranges on to a plate, and squeeze on the orange juice. Peel and thinly slice the onion or shallots and place in a single layer on the plate. Season the salmon fillets very lightly and place, flesh-side down, in the orange and onion marinade. Leave to marinate for 30–40 minutes. Heat the grill. Remove the fillets from the marinade, and place on the grill rack, skin-side up. Grill for 5–8 minutes, depending on the thickness of the fillet and how well done you like fish.
Meanwhile, strain the marinade into a shallow pan and boil until reduced and syrupy. Beat in the cubes of chilled butter, one at a time, and heat through without boiling. Divide the sauce between four heated serving plates and lay a piece of fish alongside it. Garnish with whatever you have available.
© 1995 Frances Bissell. All rights reserved.