Season the ribeye steak generously with salt and pepper.
Heat olive oil in a skillet over medium-high heat.
Add the steak to the skillet and sear for about 4-5 minutes on each side for medium-rare.
Remove the steak from the skillet and let it rest for a few minutes.
In the same skillet, add the sautéed onions and cook until caramelized.
Slice the rested steak against the grain into thin strips.
Toast the sandwich rolls lightly in the skillet.
Spread Dijon mustard and mayonnaise on the inside of each roll.
Layer the steak strips on the bottom half of each roll.
Top with sautéed onions, provolone cheese, and arugula.
Finish with the top half of the roll, serve immediately, and enjoy!