Step 1

Slice tenderloin in half crosswise to create 2 smaller roasts. If roast is untied, fold ends up against the centre/thicker part of each roast and tie with kitchen twine spaced about 1-inch apart. Make sure each halve is even in thickness.

Step 2

Chill in the refrigerator, uncovered, for 12 hours (if time allows).

Step 3

Let beef stand at room temperature for 1-2 hours before roasting.

Step 4

Arrange oven rack to the middle of your oven and preheat to 430°F (220°C).

Step 5

Season each beef tenderloin roast all over with salt and pepper. Heat the oil in an oven-proof skillet over medium-high heat until hot.

Step 6

Sear roasts on all four sides for about 3 minutes each side (about 12 minutes total), turning with tongs until well browned.

Step 7

Combine butter, garlic and Dijon (if using) together in a small bowl while roasts are searing. Set one half of the butter mixture aside to use later for the sauce.

Step 8

Slather remaining garlic butter over each roast (about 2 tablespoons each).

Step 9

Transfer skillet into the hot oven. (Alternatively: Transfer roast to a lightly greased roasting pan or baking dish.)

Step 10

Roast until an instant-read thermometer inserted into the thickest part registers 120-125°F for medium rare (about 20-25 minutes). *Or cook to your liking: 115-120°F for rare130-135°F for medium(Temperature will continue to rise about 5 degrees while the meat rests.)

Step 11

Transfer the roast to a carving board and let rest for 15 minutes. Keep the juices in the pan to make the sauce (see below).

Step 12

Carve the beef tenderloin into 1/2-inch-thick slices and serve the beef tenderloin with the optional red wine sauce.

Step 13

Skim fat off the remaining juices in the pan (if any).

Step 14

Heat oil in the same pan with remaining pan juices over medium-high heat. Sauté onion for about 3 minutes until lightly browned and softened, scraping up any browned bits left from the beef.

Step 15

Add thyme/rosemary and season with pepper. Continue cooking for a further minute or so while stirring often.

Step 16

Pour in red wine and cook until reduced by half.

Step 17

Add in beef stock and bring to a boil. Reduce heat and simmer until reduced by half. Remove the sprig of thyme or rosemary.

Step 18

Season with salt to taste and whisk in reserved garlic butter. Pour in any juices left over from the resting steaks just before serving.OPTIONAL FOR A SMOOTH AND SILKY SAUCE: strain sauce through a sieve and discard the onion before serving.