Place the fish in the preheated oven and bake for 20-30 minutes, depending on the size and thickness of your fish. Start checking to see if your fish is done at 20 minutes. Press down on the top of the salmon at its thickest part. If it feels tender but firm with some give, then the salmon is done. Once the salmon is done, take it out of the oven and let it rest in the foil for 10 minutes. You can take the salmon out of the oven slightly before it is done, as it will continue to cook while it rests.