Start by seasoning the ribeye steak with olive oil, salt, and black pepper.
Let it sit for 5 minutes to absorb the flavors.
Heat a skillet over high heat.
Add the seasoned steak and cook for about 3 minutes on each side to achieve medium-rare doneness.
Remove the steak from the skillet, and let it rest for 5 minutes.
This keeps the juices locked in and ensures tenderness.
While the steak rests, slice the ciabatta bread and toast it lightly in the oven or on a pan.
Mix the mayonnaise and mustard for a zesty spread.
Assemble your sandwich.
Layer mayonnaise mixture, sliced steak, arugula, fresh tomato slices, and caramelized onions inside the toasted ciabatta.