Preheat oven to 400 degrees f.
Line baking sheet with foil or parchment and spray with cooking spray.
Add onions and bell peppers to baking sheet.
Sprinkle with 1 tablespoon fajita seasoning, 1/4 teaspoon salt and drizzle with 1 tablespoon oil and 1 tablespoon reserved marinade.
Toss until evenly coated then spread evenly on baking sheet.
Add salmon and rub with all remaining Fajita seasoning.
Bake at 400 degrees f for approximately 12-16 minutes or until salmon is cooked through and flakes easily with a fork.
Sprinkle with fresh chopped parsley or cilantro and serve next to cooked browned rice and fresh lime wedges.