Pat steak(s) dry with paper towels; season all over with kosher salt and refrigerate until slightly dried out, about 45 minutes, if desired.

In a medium skillet over medium-high heat, heat oil. Season steak on both sides with pepper (if using). When you see the first wisps of smoke, add steak. Cook 5 minutes, then flip and add butter. Reduce heat to medium. Frequently baste steak with butter by tilting pan and spooning butter over steak. Cook until an instant-read thermometer inserted into the center registers 125° for medium-rare, about 5 minutes more.

Using tongs, hold steak upright to sear outer edges until browned, about 1 minute per side.

Transfer steak to a cutting board. Let rest at least 5 minutes. (Steak will continue to cook as it rests.) Slice against the grain; season with sea salt.

In a medium skillet over medium-high heat, heat oil. Season steaks on both sides with pepper (if using). When oil is just about to smoke, add steak. Cook 2 to 3 minutes, then flip and add butter. Reduce heat to medium. Frequently baste steak with butter by tilting pan and spooning butter over steak. Cook until an instant-read thermometer inserted into the center registers 125° for medium-rare, 2 to 3 minutes more.

Transfer steak to a cutting board. Let rest at least 5 minutes. (Steak will continue to cook as it rests.) Slice against the grain; season with sea salt.