Bring steak to room temperature before to ensure even cook
Heat a cast iron skillet over medium-high heat until hot. Add a small amount of olive oil to coat the pan. If the steak has a fat cap, start by searing the fat side first to render some of the fat.
Sear one side for 4 minutes until a deep golden crust forms. Flip and sear the other side for 2-3 more minutes for a medium doneness.
Reduce heat to medium-low and add butter, rosemary, and garlic cloves to the pan. Tilt the pan and use a spoon to baste the steak with the melted butter for about 1 minute or until desired doneness.
For accuracy, use a meat thermometer to check the internal temperature: 130°F for medium-rare, 140°F for medium, and 150°F for medium-well.
Remove the steak from the pan and let it rest for 5-10 minutes before slicing.
Notes
Steak Doneness Guide
Rare: 2-3 min per side (120-125°F)
Medium Rare: 3-4 min per side (130-135°F)
Medium: 4 min first side, 2-3 min second side (140-145°F)