A nifty "10 minutes per inch" rule applies when cooking all types of fish, but salmon can present a challenge to this rule. Salmon fillets aren't always uniform in thickness, so cooking the thickest part to complete doneness often results in thinner sections being overcooked. Another challenge is knowing how to determine doneness, since the window for cooking salmon to perfection is very slim. Cutting salmon fillets to uniform sizes, keeping a watchful eye on baking times, and paying attention to visual cues will result in beautifully cooked salmon every time.
Salmon fillets can be purchased already cut into uniform sizes, but if you have uneven fillets, simply trim off the thinner portion. If you'd prefer not to trim off the thinner portion, you can tuck it under the fillet, forming a layer approximately as thick as the rest of the fillet.
10 Minutes Per Inch
Bake salmon in a preheated, 425 degree Fahrenheit oven for 10 minutes per inch of thickness. Many salmon fillets are around an inch thick, so plan on baking it for around 10 minutes. Turn the filet halfway through, cooking 5 minutes per inch on each side.
If you prefer your salmon to be a touch rare, cook a 1-inch fillet for approximately 8 or 9 minutes. Cooking for a full 10 minutes will yield salmon that is just done, with a hint of translucency. If you prefer your salmon cooked entirely through, increase the cooking time to 11 or 12 minutes. Avoid cooking it any longer than 12 minutes, or you risk overcooking the salmon.
Whether salmon is done cooking can be largely determined by paying attention to visual cues. Salmon will turn opaque and flake easily with a fork when fully cooked. A touch of translucency will be visible near the center of the fillet for those cooked a touch rare; simply insert a knife into the center of the fillet and gently tease apart the layers to check.
If you want to be sure that your salmon is fully cooked, use an instant read thermometer inserted into the thickest part of the fillet. The United States Department of Agriculture recommends cooking salmon to an internal temperature of 145 degrees Fahrenheit. A 1-inch salmon fillet will reach this internal temperature after it has cooked for approximately 10 to 11 minutes.