Preheat oven to 300 (or BGE or WF).
Mix the brown sugar, salt, and cornstarch in a bowl.
Cut salmon into desired portions
Divide sugar mixture and sprinkle over the flesh side of the fish. Press into the fish.
Heat cast iron pan till oil smokes. Place fish in the pan, seasoned flesh side down. Cook until seasoning caramelizes, about a minute.
Turn fish and spoon some glaze over the filets. Finish in a 300 oven till desired degree of doneness achieved (about 7 minutes).