Position rack in center of oven and preheat to 450°F Place beef, fat side up, on heavy large rimmed baking sheet. Rub with oil; sprinkle generously with salt and pepper. Roast beef 20 minutes. Reduce oven temperature to 350°F Place onions around beef. Continue to roast until thermometer inserted into center of beef registers 125°F for medium-rare, stirring onions occasionally, about 2 hours 5 minutes.
Meanwhile, combine broth, Madeira, wine, thyme, parsley, rosemary, and bay leaf in medium saucepan. Boil until mixture is reduced to 2 cups, about 25 minutes. Remove from heat. Discard herbs.
Transfer beef to platter. Using slotted spoon, transfer onions to same platter; tent with foil. Let stand 30 minutes.
Pour off and reserve fat from baking sheet for Herbed Yorkshire Puddings. Scrape juices and browned bits from baking sheet into sauce; bring to boil. Mix butter and flour in small bowl to blend. Whisk into sauce; simmer until smooth and slightly thickened, about 2 minutes. Season with salt and pepper. Serve beef with sauces.