Preheat your oven to 400°F (200°C). This high temperature will help achieve a nice caramelization on the salmon.
In a medium-sized bowl, combine the melted butter, olive oil, brown sugar, soy sauce, lime juice, Sriracha, minced garlic, minced ginger, and black pepper. Whisk until the mixture is well blended and the sugar has dissolved.
Place the salmon fillets in a large baking dish. Pour the marinade over the salmon, ensuring each fillet is well-coated. For best results, let the salmon marinate for at least 15-30 minutes. If you have more time, marinate up to 2 hours in the refrigerator.
Once marinated, place the baking dish in the preheated oven and bake for about 12-15 minutes, or until the salmon flakes easily with a fork and is cooked through.
Remove the salmon from the oven, and sprinkle sliced green onions over the top for a fresh, vibrant finish. Serve immediately, drizzling any leftover marinade from the baking dish over the salmon for extra flavor.