Heat broiler on high. In a small bowl, combine the sugar and soy sauce. Set aside.

Place the salmon and sliced onion on a baking sheet covered with aluminum foil and non-stick spray. Add garlic on salmon and sprinkle salt and black pepper. Drizzle with olive oil.

Broil until the salmon is opaque throughout, 8 to 10 minutes, spooning half the soy sauce glaze over the fish during the last 2 minutes of cooking.

Serve the salmon and onion with the remaining glaze.