At least 2 hours before you’d like to make your steak, prep the steak. Liberally season all sides of the steak with kosher salt. Loosely wrap in paper towel. Place on a rack fitted in a rimmed baking sheet. Set in the coldest area of your fridge. 30 minutes before cooking, remove from the refrigerator & allow to come up to room temperature. Place a 12-inch cast iron skillet over high heat. Preheat for 5-7 minutes, until the cast iron is very hot. Meanwhile, pat the steak completely dry with paper towel. Season with ground black pepper, as desired.
Carefully add the avocado oil to skillet, adding just enough to coat the bottom of the skillet nicely. Once the oil is hot & begins to smoke, carefully place the steak on one side of the skillet. Cook for 30 seconds. Carefully flip the steak to the opposite side of the skillet & cook for 30 seconds more. Continue flipping the steak to the opposite side of the skillet in 30 second increments. Five minutes total cooking time will yield medium rare doneness.
After the last flip, reduce the heat to low. Carefully add the butter, garlic, rosemary, & thyme to the skillet. Tilt the skillet toward you, so the butter pools alongside the edge of the skillet nearest you. Use a large spoon to baste the butter over top the steak repeatedly for 30 seconds.
Transfer the steak to a plate and set aside to rest for 10-15 minutes.
Cut the steak away from the bone. Slice against the grain into 1/4-inch thick strips. Serve immediately, topped with flaky sea salt & browned butter from the pan.