To keep the cedar planks from burning, as soon as you put them on the grill, you must soak them in water for at least 2 hours. How you keep them submerged can require a little creativity. (We used a deep pan and held them down with a pineapple.) When done soaking, remove and reserve for cooking the steaks. While the planks are soaking, combine the salt, brown sugar, chopped dill, and lemon zest in a bowl.
Coat the salmon steaks with this mixture (rub) and place them on a cookie sheet in one layer. Try to coat them as thoroughly as possible.
Cover the salmon with plastic wrap and place in the refrigerator for 1 hour and 30 minutes. You are starting the cooking with a process called curing.
After 90 minutes of marinating, remove the salmon from the refrigerator and rinse off all the salt mixture.
Place the steaks into a container large enough to hold them, not necessarily in a single layer. Pour the sake over the fillets, cover them, and put them back into the refrigerator for 1 hour. After 30 minutes, give them a turn.