Pat the tomahawk dry with paper towels. Season generously with kosher salt on all sides.
Place on a wire cooling rack set over a baking sheet. Refrigerate uncovered for 24 hours.
Remove from the refrigerator 2 hours before cooking. Let it come to room temperature.
Heat avocado oil in a cast iron skillet over medium-high heat.
Sear 4 minutes per side. Remove and rest 8 minutes.
Sear 3 minutes per side. Remove and rest 6 minutes.
Sear 2 minutes per side. Remove and rest 4 minutes.
Add butter, thyme, and garlic to the pan. Once foaming, return the steak and baste 60 seconds per side. Keep that frying sound going so you don't lose temperature.
Transfer the tomahawk to a wire cooling rack set over a baking sheet.
Pour the brown butter and aromatics over the top.
Rest 5 minutes. The multi-sear and rest method builds crust slowly while keeping the inside perfectly even, with no grey band and no overcooked edge.
Slice against the grain. Plate on a platter with the bone.
Notes
Storage: cover and refrigerate leftover slices for up to 3 days. Reheat gently in a low oven to avoid overcooking, or serve cold, sliced thin.