To prevent rapid bacterial growth on salmon, it must be kept out of the "danger zone" for prolonged periods. Between thawing and cooking times, salmon shouldn't be between 40 and 90 degrees Fahrenheit for longer than two hours or between 90 and 140 F for longer than one hour. Baking and grilling are suitable ways to cook frozen salmon; both methods heat it from the frozen state, or about 0 F, to a completely cooked temperature of 145 F, which is efficient enough to stave off dangerous bacterial growth.
Frozen salmon may not cook evenly, as its outer flesh thaws sooner than the center. This can yield overcooked exteriors and may be a problematic if a filet has a thin and a thick side; normally, the solution is to fold the thin side underneath to make a piece of uniform thickness, but of course you can't do that to a frozen cut. Also, you can't effectively season frozen salmon. Salt, pepper and other aromatics, spices and herbs won't stick to it, and a marinade can't penetrate frozen flesh. You'll have to wait to add flavoring agents until your salmon is partially or fully cooked.
Safe Ways to Thaw
Plan ahead and thaw salmon by moving it into the refrigerator a day or two ahead of time. For faster defrosting, soak it in a cold-water bath for one to two hours. Seal the salmon in a leak-proof bag if it isn't already in airtight packaging and replace the water every half hour to keep it cold. Your microwave's defrost function is a third option that takes only a few minutes. However, the microwave begins cooking the outer meat, so it may turn out overcooked in the end.
Baking Frozen Salmon
Preheat the oven to 325 F. It's standard to cook salmon at a higher temperature, but heating it more gently minimizes or prevents the outer flesh from overcooking. Place a greased sheet of foil or parchment paper on a baking tray and put the salmon steak or filet on top. Because it's frozen, the estimated cooking time is extended by around 50 percent. So bake the fish for approximately 22 to 32 minutes, depending on its thickness. It's finished when the flesh is flaky and opaque all the way through.
Grilling Frozen Salmon
Preheat the grill to medium heat, rather than the more typical moderately high temperature, to gently cook it. Scrape the grill clean and grease it thoroughly. Place the salmon presentation-side down first, so it can develop attractive grill markings. Because cooking time is about 50 percent longer than the time it takes for defrosted salmon, cook the frozen filet or steak for about 5 to 7 minutes per side, just until the inside is entirely opaque and flaky.