Place a large sheet of foil on a large rimmed baking sheet. Place salmon fillets, skin-side down, in the middle of the foil. Pat the salmon dry with paper towels. Brush or spoon half of the maple mixture (about 1/4 cup) evenly over the salmon; set aside the remaining maple mixture. Bring the edges of the foil together over the salmon and crimp tightly to contain the maple mixture in the foil. Bake until the salmon just starts to turn opaque, 12 to 15 minutes. Remove from oven; open the top of the foil to expose the salmon, but keep the foil edges upright to contain the maple mixture. Pour the reserved remaining maple mixture over the salmon. Return the pan to the oven and turn the broiler to high. Broil until the salmon starts to brown in places, about 5 minutes.