Preheat the oven to 400˚F. Line a baking sheet with aluminium foil and set aside.
Place the salmon filets on the baking sheet. Pat them down with paper towels and drizzle with the olive oil.
In a small bowl, mix together the brown sugar, onion powder, cayenne pepper and salt.
Sprinkle the spice mixture on top of the salmon and bake in the preheated oven for 15 minutes. Turn your oven to broil and cook the salmon for an additional 1-2 minutes.