Heat the oven to 400°F. Heat the oil in a large, oven- and flame-proof sauté pan on the stovetop until the oil is very hot, but not smoking.
Season the fish on both sides with salt and pepper and dust with Wondra flour. Blow off excess.
Put the fish in the pan, skin side down, and press down on the fish with a spatula. (The skin immediately contracts and buckles, but you want to keep it all in contact with the pan for maximum crisping.) Sear on the stovetop over medium heat until golden brown on the bottom, about 3 minutes.
Turn the fish over, put the pan in the oven, and cook another 2 to 3 minutes, until a metal skewer can be easily inserted into the center of the fillet and, if left for 5 seconds, feels just warm when touched to your lip. Serve immediately.