Searing the beef tenderloin roast in a skillet gives a lovely browned appearance to the meat and seals in the flavorful juices. Fresh peppercorns, thyme, and bay leaves steep in the red wine and onion gravy imparting subtle but savory flavors.
Heat oven to 450°F.
Heat a large stainless steel skillet (not nonstick) over high heat until very hot. Add vegetable oil. Season all sides of the meat with salt and pepper. Place meat in the skillet and brown on all sides, about 6 minutes total. Remove to roasting pan with rack.
Roast at 450°F for 25 to 30 minutes or until internal temperature registers 5°F less than desired finished temperature on an instant-read thermometer.
Meanwhile, in a medium-size heavy bottomed saucepan, cook onion over medium heat in 1 tablespoon of the butter for 3 minutes until softened. Add red wine, peppercorns, bay leaf and thyme. Bring to a boil; boil for about 4 to 5 minutes until syrupy consistency. Add broth and simmer for 2 minutes. Strain and discard solids. Pour liquid back into saucepan.
In a small dish, mix together remaining 3 tablespoons butter and the flour with your fingers until combined and somewhat crumbly. Gradually whisk into simmering sauce until thickened. Remove sauce from heat; keep warm.
Remove meat from oven and allow to rest in a warm place 10 minutes before slicing. To serve, thinly slice meat; whisk sauce over low heat, if necessary to reheat, and serve with meat.