The unsaturated fat and high moisture content in salmon's flesh make it a delicious, nutritious fish. Having such good starting material makes it easier on you, the cook. Your number one priority in protecting the quality of the fish is not cooking it too long, since that dries it out. Preparing the salmon in the oven is easier than cooking it on the stove top or grill. Cooking it at low temperature with moist heat helps it remain succulent and tender.
Select fresh salmon with a mild smell, clear and slightly bulging eyes, shiny flesh and bright red gills and no discoloration or dry edges if you're not buying frozen. Fresh fish should never smell too fishy, sour or like ammonia. If buying frozen, avoid torn or otherwise damaged packages and fish showing signs of frosting or freezer burn.
Move frozen salmon into the refrigerator the day before you're going to cook it so it defrosts. If you aren't prepared ahead of time, thaw the salmon by immersing it in a bowl of cold water, provided it's sealed in a leak-proof package. This method only takes about an hour or two. Every 30 minutes, empty the bowl and refill it with colder water. If you don't even have this much time, turn to the defrost function of your microwave.
Put a rack on the lowest tier of your oven and place another just below center so the salmon is in the middle of the oven when it cooks. Preheat to 250 degrees Fahrenheit, starting at least 20 minutes before you put in the salmon.
Fill a cake tin, baking dish or other oven-safe vessel about halfway with water, stock, broth or white wine. Place it on the bottom rack of the oven when you turn it on. The steam will help keep your salmon tender during baking.
Wash away any scales by holding the salmon under cold faucet water. Dry thoroughly with clean paper towels.
Place a wire rack on a baking sheet. Grease the rack with nonstick spray or cooking oil.
Coat the salmon with cooking oil or melted unsalted butter using a brush. Apply salt and pepper to taste, along with any other desired herbs or spices. Add texture, if you like, by selecting sea salt or coarse kosher salt rather than table salt and coarsely ground pepper.
Put the salmon on the wire rack, which elevates the fish to allow hot air and steam to circulate all the way around it. Put it onto the oven tier right below center.
Bake the salmon for about 25 minutes. Cooking time varies, however, based on the thickness of your cut of salmon, the consistency and accuracy of your oven temperature and other considerations. To determine if the fish is fully cooked, cut into the center of the fillet or steak with a fork. The flesh should flake without resistance, and it should look opaque all the way through. Fish doesn't need to rest like meat, so serve it right away.