Season your steaks with kosher salt and return to the refrigerator for 2-4 hours if possible, but at least 30 minutes.
In a shallow pan or plate, mix together the flour, black pepper and Aleppo pepper, set aside.
Heat the oil in a cast iron pan, over medium high heat. As oil is heating up, dredge the steaks in the flour mixtures, ensuring both sides are evenly coated. Preheat the oven to 325°F.
Gently lay the steaks in the hot cast iron pan. You may need to fry them in batches to avoid overcrowding. Sear them for two minutes on each side.
Reduce the heat to medium, and add the butter and onions to the pan. When butter melts, add two tablespoons of the flour mixture and move the onions around to cook down the raw flour.
Add the beef stock and bouillon to the pan, and bring to a boil. Add the cornstarch slurry and Worcestershire sauce, whisking until the gravy starts to thicken.
Add the steaks back into the pan and spoon the gravy on top of steaks. Place the pan into a preheated oven for 25 minutes. garnish with parsley, and serve with potatoes and green beans.