To keep the cedar planks from burning as soon as you put them on the grill, you need to 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 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 by a process called curing.
After the 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 and put back into the refrigerator for 1 hour. After 30 minutes, give them a turn.