Knowing how to cook salmon in the oven is essential to mastering basic cooking techniques for weekday meals. Preheat the oven to 450 degrees F for fillets, or 350 degrees F for a dressed fish. Fillets can be baked at a lower temperature, if desired, with an increase in cooking time. Bake salmon fillets or steaks, uncovered, for 4 to 6 minutes per 1/2-inch thickness. Bake a dressed salmon for 6 to 9 minutes per 8 ounces of fish. To test for doneness, insert a fork and gently twist. The salmon is done as soon as it begins to flake and becomes opaque.