Season fillets with salt and pepper, onion powder, and red pepper flakes. Set aside in a baking dish.

In a medium bowl, mix together olive oil, lemon juice, garlic, balsamic vinegar, sugar, green onions, and cilantro. Pour marinade over salmon; cover, and refrigerate overnight, or at least 6 hours.

Preheat oven to 450 degrees F (230 degrees C).

Arrange salmon on a broiling sheet. Place in a preheated oven, and bake for 5 minutes. Increase heat to 500 degrees F (260 degrees C), turn fillets, and broil 5 minutes more.