Step 1

Melt 5 tablespoons of the butter in a medium saucepan. Add the shallots and cook over medium-low heat, stirring occasionally, until soft and translucent, 7 to 8 minutes. Add the wine, beef broth, thyme sprigs, salt, pepper and sugar, and bring to a boil. Cook over medium heat for about 30 minutes, or until the liquid is reduced by about half.

Step 2

While the liquid is reducing, place the remaining 3 tablespoons of butter in a small bowl and soften in the microwave, if necessary (it should be soft but not melted). Add the flour and, using a small spoon, mix into a smooth paste.

Step 3

Once the wine mixture is reduced, reduce the heat to low and remove the thyme sprigs. Whisk the flour-butter paste, a tablespoon at a time, into the simmering liquid, and simmer for a few minutes, until the sauce is thickened. Set aside. (The sauce can be made up to this point and refrigerated up to 3 days ahead of time.)

Step 4

Let the beef stand at room temperature for 1 hour before roasting. Set an oven rack in the middle position and preheat the oven to 400°F.

Step 5

Season the beef all over with kosher salt and pepper. Heat the oil in an oven-proof skillet over medium-high heat until almost smoking. Cook, turning with tongs, until well browned on all but one side, about 10 minutes total. Turn the tenderloin so that the un-seared side is down, and transfer the skillet directly to the preheated oven. (If your pan isn't oven-proof, transfer the beef to a lightly oiled roasting pan.) Roast until a thermometer inserted into the center of the meat registers 120°F-125° for medium rare, about 15 minutes, or until done to your liking (115°F-120°F for rare, 130°F-135°F for medium). Keep in mind that these temperatures account for the fact that the temperature will continue to rise about 5 degrees while the meat rests.

Step 6

Transfer the meat to a carving board (preferably with a well for collecting juices) and let it rest, covered loosely with aluminum foil, for 10 to 15 minutes. Place a dishtowel or oven mitt over the handle of the roasting pan to remind yourself that it's hot.

Step 7

Meanwhile, carefully discard the fat from the roasting pan (remember that the handle is hot!). Set the pan on the stovetop and add the ¼ cup of broth. Bring the broth to a boil and, using a wooden spoon, scrape the fond, or brown bits, from the bottom of the pan. Add the flavorful broth to the red wine sauce, and then bring the sauce to a simmer.

Step 8

Carve the tenderloin into ½-inch-thick slices. Serve the beef, passing the red wine sauce at the table.