How to Make It
Combine 2 1/2 cups hot water, brown sugar, salt, and onion powder in a large bowl, stirring until sugar and salt dissolve. Stir in 2 1/2 cups cold water. Place salmon in a 13- x 9-inch baking dish, skin side down. Make 2 long lengthwise slits in the flesh of the fillet, leaving the skin intact. Pour brown sugar mixture over salmon, and chill, uncovered, 1 hour.
Place a wire rack in a rimmed baking sheet; transfer salmon to rack. Pat salmon dry with paper towels. Brush flesh with Pernod, and chill, uncovered, 2 hours.
Light 15 to 20 briquettes in a charcoal chimney starter. When the briquettes are covered with gray ash, pour onto bottom grate of a charcoal grill, then push briquettes to 1 side of the grill grate. Scatter a handful of wood chips (preferably alder wood) over the top of the briquettes. Coat the top grate with oil; place on grill.
Lightly coat salmon skin with cooking spray. Place salmon, skin side down with head to tail ends parallel with the grill grates, on oiled grate, as far from hot coals as possible. Close the vent opening at the bottom of the grill by half; close the top vent opening in the grill lid by half. Grill salmon, covered and maintaining grill temperature between 200°F and 225°F, until salmon is a rusty reddish-brown and a small amount of protein has coagulated, leaving little white dots on the fish, 45 to 60 minutes. Using 2 spatulas, carefully tilt the tail end of the salmon up so excess juices run out; transfer to a serving platter. Serve warm or at room temperature.