In a small bowl, mix together the next five ingredients. Rub the spice mixture on salmon generously, so that the surface is covered. Allow it to marinate with the rub for 30 minutes.
Meanwhile, light the grill to medium high. Remove the plank from the water and place filets on the cedar plank, skin side down. Transfer the plank to the hot grill rack. Cover the grill and cook for 20-25 minutes.
When the salmon is done, transfer the plank to a metal serving platter, making sure that the cedar is not burning. If the cedar is burning, keep a spray bottle with water handy to extinguish any flames.
Garnish with lemon and thyme sprigs.
Notes
When you’re through, wash off the used cedar and break it into pieces. Then, throw the pieces directly on hot coals when grilling, to impart the wonderful cedar flavor to other foods.