Preheat oven to 425 degrees (F).
Line a 13" x 9"-inch baking dish with foil. Coat with nonstick cooking spray. Place fillets in the dish, skin side down if applicable.
Combine brown sugar, maple syrup, soy sauce, mustard, and pepper. Pour over the fillets.
Bake for 20 minutes or until fish flakes easily with fork. Baste the salmon with the syrup mixture halfway through baking time.
Serve salmon with syrup mixture drizzled over fillets.