Remove meat from the refrigerator about an hour before cooking to let it rise to temperature. Pat the meat dry.
If your butcher did not tie your meat, tie it at 1” intervals down the length of the cut. Use pieces of kitchen string about 12” long and tie each around the meat so the string is snug but not tight.
Slice the onion; scrub and cut the carrots.
Stir together the cornstarch and the 2 tablespoons of red wine.
Preheat the oven to 400° F.
Arrange the sliced onion and carrot pieces in the bottom of the roasting pan.
Place the roast fat side down on top of the vegetables and sprinkle with kosher salt and freshly ground pepper. Using a probe thermometer, insert the probe into the middle of the thickest part of the roast.
Place the roasting pan, uncovered, in the preheated oven and immediately turn the temperature down to 325° F. Roast at 325° F for 45 minutes, then turn the heat down to 200° F.
Remove meat from the oven when the internal temperature reaches 125° F for rare, 130° F for medium-rare, and 140° F for medium.
Place the meat on a wooden cutting board or a warmed serving platter and cover loosely with foil. Let rest for about twenty minutes. The temperature will continue to rise as the meat rests.
While the meat is resting, place the roasting pan over medium-high heat on the stovetop. You might need to turn on two burners. Bring the pan juices to a boil and cook until the liquids are almost all evaporated and the onion and carrot begin to fry in the beef fat. Make sure to stir constantly and scrape all over the bottom of the pan with a metal or wooden spatula. Carefully spoon off/pour off as much of the remaining fat as possible. Put the pan back over medium-high heat and add the wine and smashed garlic. Cook, scraping the bottom of the pan to thoroughly deglaze until the wine has been reduced to only a tablespoon or two. Add the beef stock along with the tomato paste and thyme. If using fresh thyme, throw the whole sprig in, as you’ll be straining the sauce before serving.
Bring all this to a rolling boil and stir in the wine/corn starch mixture (slurry). Turn the heat down a bit and boil gently until the sauce has thickened somewhat and the raw starch flavor has been cooked out. Taste the sauce and adjust the seasonings by adding a little kosher salt and/or freshly ground black pepper if necessary. Strain the sauce through a fine mesh strainer, pressing down on the solids. Swirl in 1 tablespoon of butter to add a bit of richness and a nice sheen to your sauce.
Remove the foil from the roast, cut off and remove the strings. Trim off as much of the surface fat as you’d like, and then slice, passing the sauce at the table.
