Soak the cedar plank in cold water for at least 2 hours. Place the salmon in a single layer in a shallow dish. Place the citrus zest and juice, the pepper, oil and honey in a bowl and whisk to combine. Pour over the fish and turn the fillets to coat. Cover and marinate in the fridge for one hour, turning occasionally.
Preheat your barbecue to medium-high. Remove the plank from the water and pat dry one side. Set the fish on the plank, season with salt, and then place the plank on one side of the barbecue. Turn the heat underneath the plank to low, leave the other side of the barbecue set at medium-high.
Close the lid and cook the salmon for 15 to 18 minutes, or until just cooked through. Keep a spray bottle of water
handy in case the board ignites. Set the plank on a serving tray, garnish with citrus slices, and serve.