Heat 2 tablespoons olive oil in a large cast iron or nonstick skillet over medium-high heat until just starting to smoke, 2 to 3 minutes. Add the halibut and sear undisturbed until well browned on the bottom and the sides are cooked just past halfway up the fillets, 4 to 5 minutes. Reduce the heat to medium, flip the fillets, and cook until just cooked through and the flesh flakes easily, 3 to 5 minutes more. Transfer to a serving platter or individual plates.
