Take the steak out of the refrigerator and season it with kosher salt. Let it sit at room temperature for about 60 minutes. If available, trim a small piece (approximately 1" square) of fat from the outer edge of the steak.
Start your grill or stovetop and prepare it for high direct heat.
Place your cast iron skillet or griddle directly over the high heat source and let it get blazing hot. It's important to preheat for 5-10 minutes to ensure it's scorching.
In the hot pan, add the small piece of beef fat that you trimmed from the steak. Let it sizzle for about 30 seconds, creating a slick, oily surface. If you don't have the beef fat, Wagyu tallow is a suitable alternative.
Carefully place the Wagyu steak into the rendered fat and resist any temptation to move it. Cover and allow it to cook for two minutes.
Flip the steak, cover, and cook for an additional two minutes. Then, use a reliable quick-read thermometer to check the internal temperature. It should read around 115°F.
Remove the steak from the heat and transfer it to a warm plate.
Gently tent the steak with foil and let it rest for about three minutes before slicing. Taste and, if needed, add a pinch more salt. Serve and savor the deliciousness.