How Long to Cook Pan-Seared Halibut Fillet (1-inch, Skin-Off) in the cast iron
Specification: 6–8 oz skin-off halibut fillet, about 1-inch thick at the thickest end, patted bone-dry on both faces and salted 15 minutes before cooking (do not brine longer — halibut is very lean and will over-salt)
3-Step Execution Protocol
Heat cast iron skillet over Medium-high (surface ≈425°F) with 1 tbsp neutral oil and 1 tbsp butter added after the first flip until lightly smoking. Prepare pan-seared halibut fillet (1-inch, skin-off) (6–8 oz skin-off halibut fillet, about 1-inch thick at the thickest end, patted bone-dry on both faces and salted 15 minutes before cooking (do not brine longer — halibut is very lean and will over-salt)).
Cook for 5–7 mins (3–4 mins on the first side, 2–3 mins on the second side with a butter baste). Flip at the 3-minute mark for even browning.
The first side is a firm even brown with no white bead of albumin on the top face; the fillet flakes cleanly along the natural muscle lines when nudged with a fork, and the centre is opaque all the way through with no translucent grey band. Confirm internal temperature reaches 130°F (pull) → 135°F FDA/NOAA-recommended fish target after 3-min rest — halibut goes from tender to chalky above 135°F. Rest for 3 minutes before serving.
FDA/NOAA recommended internal temperature of 145°F for fish is the food-safety maximum; 130–135°F pull-and-carryover for lean flatfish like halibut per Serious Eats "How to Cook Halibut" and America's Test Kitchen halibut reference — both attribute the chalky texture at the FDA number to the very low fat content of halibut (~1 g fat per 4 oz raw). Fifteen-minute salt cure per Cook's Illustrated lean-fish technique note (longer draws too much moisture and dries the flesh).