One of the easiest ways to prepare fish is under low heat. Chef Samin Nosrat writes in her book “Salt, Fat, Acid, Heat,” that using a softer heat when preparing fish helps to prevent overcooking (via The Washington Post). Roasting a delicate white fish filet in the oven at 250 degrees significantly lowers the chances of you overcooking your fish because it raises the internal temperature at a much slower rate. Sadly, this does mean a cooking time of roughly 35 to 40 minutes depending on the cut of the fish, but your patience will also be rewarded by a juicy and delicate meal. Unilateral cooking is another great method for slowly preparing a delicate and delicious fish dinner.
Nosrat adds that this method works especially well with fattier cuts of fish like salmon. That abundant fat will render as the fish cooks, and add a boost of flavor.
It should be noted that the United States Department of Agriculture recommends cooking fish to an internal temperature of at least 145 degrees Fahrenheit, but this might be overdoing it for many fish. Harold McGee writes in “On Food and Cooking” that most fish will start to tighten up and release their moisture around 120 degrees (via The Washington Post). That means that it’s best to remove the fish from heat and let its internal temperature rise on its own before it dries out.