Remove the T-bone steak from the refrigerator and let it sit at room temperature for 40 minutes.
Brush the steak with olive oil and season generously with salt and black pepper.
Preheat the grill to high heat (450°F / 232°C) or heat a cast-iron skillet over high heat until smoking hot.
Place the steak on the grill or skillet, searing for 2-3 minutes per side to develop a crust.
Move the steak to indirect heat or lower the skillet’s heat. Continue cooking for another 4-5 minutes per side or until the internal temperature reaches 130°F (54°C) for medium-rare.
Add butter, minced garlic, and rosemary to the skillet. Spoon the melted butter over the steak for extra flavor.
Remove the steak from heat and let it rest for 5-10 minutes before slicing.
Slice against the grain and serve with your favorite sides.
Notes
For extra tenderness, dry brine the steak by seasoning with salt and leaving it uncovered in the fridge for 24 hours before cooking.