In a medium bowl, combine the steak, olive oil, garlic powder and generous amount of salt and pepper. Massage the seasoning and oil into the steak until the steak is well coated.
In a cast iron pan on a medium – high heat, melt the garlic butter. Once the butter is melted and frothing, place the steak into the pan and sear on each side for 1 minute for medium rare or until cooked to your liking. The steak will form a beautiful crust. This step may need to be done in batches so you do not overcrowd the pan. Remove the steak from the pan and set to the side.
Add the red onion to the pan and cook for 2 minutes, stirring consistently. Add the Worcestershire sauce to the pan and cook for 30 seconds.
Add the steak back to the pan and stir through the sauce for 30 seconds. Take off the heat and stir through the parsley. Serve immediately with some fresh bread, salad or potato mash.