Soak cedar planks in water for 4 to 6 hours. (This is essential to make sure planks do not catch fire, so don't skimp on this step)
Preheat grill to high.
Season the soaked planks with salt and pepper and place on the grill for 3 to 5 minutes with lid closed. They will begin to crackle and smoke.
Place salmon fillets carefully on cooking planks, skin side of the fish on the plank. Close the lid and bake the fillets for 12-15 minutes. Check periodically to make sure cooking planks have not caught fire.
Have a spray bottle of water on hand to spritz planks in case they do, but it is much less likely to happen if they have been well soaked beforehand.
Remove cooking planks from grill and squeeze lemon juice over salmon fillets and top off with your favorite Hollandaise recipe or mix (I use Knorr and add dill weed).