Soak cedar planks in salted water for 2 hours then remove and drain.
Rinse the salmon under cold running water and pat dry with paper towels. Carefully remove any remaining pin bones.
Combine orange juice, orange zest, rosemary and plum wine in a small sauce pan. Place over medium high heat and reduce by 1/2 to create a light glaze.
Lay the salmon on the cedar plank and carefully brush with the orange plum wine glaze saving some for later.
Prepare grill for indirect grilling and heat to medium high. Place the cedar plank with the salmon on the hot grate away from the heat.
Close the grill lid and cook for about 15 minutes then take a sharp knife and make a couple of cuts on the fillet (while still on the plank) and separate slightly to expose the meat to the grilling heat. Brush on the remaining glaze mixture.
Close the lid and continue cooking for another 10 to 15 minutes or until cooked through. (depending on the thickness of the fillet) The internal temperature should read 135 degrees F.
When ready transfer the plank with the salmon to a heat proof surface and serve right off the plank.