• Preheat the oven to 425°F / 220°C.
• Tie the roast with cooking twine and season each side generously with salt and pepper.
  
• Preheat a cast iron skillet over medium heat. Add two tablespoons of olive oil and bring it to the smoke point, then sear the roast on all sides. Remove the roast from the heat.
  
• In a small bowl, mix together the rosemary, thyme, garlic, salt, pepper and the remaining three tablespoons of the olive oil. Rub the herb and garlic mixture all over the roast.
• Place the cast iron skillet in the preheated oven for 15 minutes. Decrease the temperature to 300°F / 150°C and roast it for approximately 45 minutes, or until the internal temperature has reached 130°F / 55°C. (At this point the roast will be medium-rare. It will continue to cook after being removed from the oven, so the temperature will rise an additional 5 to 10 degrees.)
• Remove the roast from the pan and tent it with foil. Pour off the excess grease from the skillet.

Red Wine Mushroom Sauce

• Return the skillet to medium heat and melt two tablespoons of the butter. Add the onions and sauté until they’re translucent. Add the mushrooms, season them with salt and pepper, and cook them for another 5 minutes or until the liquid they release has been cooked off.
• Deglaze the pan with the red wine and cook until it has been reduced by half. Add the beef broth and fresh thyme, and cook until the sauce has reduced by about two-thirds. Stir in the remaining cold butter to finish the sauce, and spoon it over slices of the roast beef.