Heat the grill to medium-high.

Layer two large sheets of aluminum foil and fold in the edges to make "sides". Place the salmon fillets on the foil sheets. Spread a thin coating of butter on the filets. Sprinkle on a dusting of the lemon pepper. Then sprinkle the top with brown sugar.

Place the salmon fillets on the grill, cover, and cook 4 to 6 minutes per 1/2-inch thickness, or until the fish flakes easily when tested with a fork. Serve immediately.