You don't say if it's whole or fillet? However I will proceed on the assumption of a whole Salmon. All I do is in the cavity I spread a generous amount of unsalted butter, season with sea salt a freshly ground black pepper. I do the same to one side of the fish, turning it over and placing into a baking dish. Butter and season the remaining side and add sprigs of thyme and rosemary in the cavity, squeeze of lemon over the fish, also the cavity.
Tent with foil, into a preheated oven starting at 400F, then bring down to 325F after 15 minutes. There is no need to open the oven at all for 25 minutes (Talking good size salmon here, less time if smaller), after time lapses, remove tent (foil) and allow further 15 minutes. Use skewer, and pierce in thickest part of the fish, the skewer should come out clean, if so it's ready.
Use the juices in the pan to baste.
Might be an idea to spray your baking dish first off with PAM or something similar. Should have mentioned it first off.
Enjoy the natural flavors of the sea....
Chris