Soak the cedar plank in cold water for at least 2 hours. With a sharp, narrow knife, cut a 3" slit into the centre of each salmon fillet. Divide and stuff the shrimp into the salmon fillets.
Preheat your barbecue to medium-high. Remove the plank from the water and dry one side. Set the fish on that side of the plank. Combine the lemon juice, oil, honey and tarragon or dill in a small bowl. Brush the mixture over the fish; season with salt and pepper. Set the plank on one side of the barbecue. Turn the heat underneath the plank to low; leave the other side of the barbecue set to 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 plank ignites.