I laid the filet skin-down on a large foil sheet, drizzled it with truffle oil, covered it with the seasoning, covered it with onions, covered the onions with the seasoning, sealed the foil, and roasted it for 15 minutes at 500 degrees F.
From the first onion, it was heaven. The onions picked up the flavor of the salmon, and vice-versa, in a good way. It would have been great without the seasoning, but the seasoning made it greater. I think the truffle oil made it the greatest. The fish was moist, flaky, and perfectly cooked. I’m making it again tomorrow.