Squeeze the orange extracting about 200mls of orange juice into a pan. Add the honey, soy sauce, muscovado sugar, garlic and ginger to the pan.
Place on medium heat, stirring occasionally for approximately 5 minutes until the sugar has dissolved. Take off the heat and allow the marinade to cool. Preheat your oven to 200 degrees Celsius or 180 degrees Celsius if using a Fan-assisted oven.
Cut out a rectangular piece of foil which you will use to cook the fish. Make sure it is large enough to enclose the fish completely. Baste the salmon fillets with the marinade, and then place your fish on the cut-out foil. Pour the rest of the marinade into the foil.
Place a slice of orange and a dollop of butter on the fillet, then wrap the foil around the fish enclosing the fish in the tent while leaving a little opening at the top of tent for the air to escape. Bake in the oven for 20 minutes.