Kosher salt
2 tbsp butter
1 tsb garlic powder
1 tbsp dry rosemary
Canola oil
Onion, diced (optional)
Wire rack in a sheet pan
Oven safe, high heat safe skillet (such as cast iron)
Lid or splatter guard is recommended for the skillet
Oven/stove
Prep the ribeye: At lest 24 hours before cooking generously cover the ribeye on all sides with kosher salt. Place the ribeye on a wire rack which is in a sheet pan (the wire rack allows for air flow and the sheet pan catches any mess) Place uncovered in the refrigerator.
Make the butter: At about the same time preparing the ribeye soften the butter mix then in the garlic powder, rosemary, and black pepper. Refrigerate until needed.
Cooking the ribeye: About 2 hours before cooking remove the ribeye form the refrigerator and allow it to warm to room temp. Rub the ribeye with canola oil and add more kosher salt. Preheat the oven to 400 °F. Put oil in the skillet and heat on high until it is smoking. Cook the ribeye on high for 2-3 minuets. Flip the ribeye put the herb butter on top and cook on high for 2-3 minuets. Move the skillet (uncovered) to the oven for 3-5 minuets. Move the ribeye to a plate covered with a bowl to rest for 10 minuets, note you may need to spread out the rosemary as it may clump up where the butter was. In the mean time return the skillet to the stove and cook the diced onion on medium low until caramelized.