Season and rest. Pat the steaks very dry with paper towels. Season all sides generously with salt and pepper. Let them sit at room temperature for 30 minutes.
Heat the skillet. Heat the cast iron skillet over medium-high heat for about 5 minutes, until very hot. Add the oil. The pan is ready when the oil shimmers and just starts to smoke
Sear the first side. Lay the steaks in the pan, placing them away from you. Leave space between them, and cook in batches if your skillet is crowded. Sear without moving them for 4 minutes, until a deep brown crust forms and the steaks release easily.
Flip once. Flip the steaks and cook 2 minutes. Use tongs to hold each steak on its fat-cap edge against the pan for 30–60 seconds to render the fat.
Butter baste. Lower the heat to medium. Add the butter, garlic, rosemary and thyme. Tilt the skillet toward you and spoon the foaming butter over the steaks continuously for 1–2 minutes. Stop when the thermometer reads 5°F below your target doneness (125°F for medium-rare).
Rest. Move the steaks to a cutting board and spoon the garlic butter over the top. Rest them for 5–10 minutes. The temperature will rise about 5°F as they rest.
Slice and serve. Slice against the grain and serve with the pan butter spooned over the top.