Remove the T-bone steak from the refrigerator and let it sit at room temperature for 30 minutes before cooking.
Preheat the oven to 450°F (230°C).
Pat the steak dry with paper towels, then season both sides generously with Kosher salt, cracked black pepper, and dried Italian seasonings.
Heat the cast iron skillet over high heat and add the olive oil, coating the pan well.
When the skillet is very hot, place the steak in the pan and sear for about 3 minutes on each side until a golden-brown crust forms.
Carefully transfer the skillet to the preheated oven and roast until the steak reaches your desired doneness (about 6–8 minutes for medium-rare, about 130°F/54°C).
Remove the steak from the oven and transfer to a cutting board. Let rest for 10 minutes before cutting the meat from the bone and slicing across the grain.
If using, top the steak with compound butter and garnish with fresh herbs before serving.