Allow the steak to rest on the counter for at least 30 minutes before cooking. Preheat the oven to 350 degrees.
Prepare all ingredients, and set aside. Heat the cast iron pan over medium high heat. Pat the steak dry, and season with salt and pepper (or steak seasoning, if desired.) Add in the oil, and when it starts to shimmer, add in the steak, allowing it to sear for 3-4 minutes and develop a deep golden brown crust. The steak should release naturally from the pan. Flip the steak and repeat.
Place the pan with the steak into the pre-heated oven to finish, until it reaches your desired doneness – about 5 minutes. Remove the pan, and place the steak onto a plate to rest for at least 5 minutes before serving.
Toast the sliced ciabatta rolls, and combine the mayonnaise and dijon together in a small bowl. Smear onto the ciabatta bread, then top with arugula. Slice the steak thinly, and divide into the sandwiches. Top with crumbled cheese, sliced shallots and drizzle with balsamic glaze. Top with other half of the ciabatta roll and serve.