Preheat your oven to 375°F (190°C) and line a baking dish with aluminum foil for easy cleanup.
In a small bowl, whisk together the brown sugar, soy sauce, olive oil, minced garlic, grated ginger, black pepper, and red pepper flakes (if using) until well combined.
Place the salmon fillets in the prepared baking dish, skin side down. Pour the marinade over the salmon, ensuring it is evenly coated.
Let the salmon marinate for at least 15 minutes at room temperature, or for up to 1 hour in the refrigerator for more intense flavor.
Bake the salmon in the preheated oven for 15-20 minutes, or until the salmon flakes easily with a fork and reaches an internal temperature of 145°F (63°C).
Remove the salmon from the oven and let it rest for a few minutes. Garnish with sliced green onions before serving.
Notes
For a sweeter glaze, increase the brown sugar to 1/3 cup.
Serve the salmon over a bed of steamed rice or quinoa for a complete meal.
You can also add steamed broccoli or asparagus on the side for extra vegetables.