Remove the steak from the refrigerator and allow the meat to come to room temperature, approximately 20 minutes. Pat the meat dry with a kitchen towel which will help to develop a crust when cooking.
Pour the sunflower oil over the steak and season well with salt, then rub the oil into the meat using your hands.
Place a large sauté pan on a high heat and allow it to come up to temperature. Then add the steak to the pan and sear for 2 minutes without moving the meat.
After 2 minutes flip the steak and cook for 2 minutes more on the opposite side. Rare - 1 minute each side, Medium Rare - 1 ½ minutes each side, Medium - 2 minutes each side, Well Done- 4 minutes each side.
A dark crust should have developed on either side of the steak, check the cooking with your finger (firm with a bit of a spring) or a meat thermometer.
Remove the pan from the heat and add the butter, garlic, thyme and rosemary. Baste the butter over the steak then transfer the steak to a plate and pour the contents of the pan over the meat.
Cover the steak with a kitchen towel and allow to rest for 5 minutes.
Once rested, serve the perfectly cooked medium sirloin and season with freshly cracked black pepper.
Notes
Not all of the fat will be consumed, especially the peanut oil used for cooking. This has been considered in the macro calculations for this recipe.