Freeze the ribeye for 30 minutes, then slice it across the grain as thinly as possible with a sharp knife.
Heat half the oil on a large griddle or cast-iron skillet over medium-high heat and cook the onion with 1/4 teaspoon salt for 7 to 9 minutes until browned at the edges.
Move the onion to a plate, add the remaining oil and spread the beef in one loose layer so it sears instead of steaming.
Season with the remaining salt and black pepper, cook for 2 minutes, then turn and chop the beef into broad bite-size ribbons until it reaches 145°F.
Divide the beef into four piles, mix onion into each pile and cover each with two provolone slices until softened.
Scoop each pile into a roll, close the sandwiches and rest them for 2 minutes so the bread catches the juices without becoming soggy.
