Lay the salmon fillets in a baking dish and spread evenly with brown sugar. Sprinkle with garlic powder, soy sauce and lemon juice. Cover tightly with plastic wrap, refrigerate and allow to marinate for up to 8 hours. Preheat the oven to 350*. Bake, uncovered, for about 15 minutes. Baste occasionally with the juices that accumulate in the pan. This salmon is also excellent barbecued over medium coals.