Put the skillet in the oven and roast until an instant-read thermometer registers 130 degrees F, about 40 minutes. Remove the roast from the oven to a cutting board and let rest for 10 minutes. Remove the onions and mushrooms from the skillet.
06While the beef is resting, prepare the gravy.07Put the skillet on low heat. Add the wine and stock, while scraping up the browned bits on the bottom of the pan. Whisk in the flour until the sauce is thickened and smooth.08Slice the beef into very thin slices. Transfer to a platter and serve with the mushrooms, onions and gravy.