Step 1

Halve the beef tenderloin into two equal portions to make two roasts.

Step 2

Tie each piece snuggly with strands of kitchen twine at 1-inch intervals, while tucking thinner tail end under if there is one to create a roast with even thickness so it cooks evenly.

Step 3

Season each portion liberally with kosher salt (I use 2 Tbsp total, but season to your preference).

Step 4

Place on a wire rack set over a rimmed baking sheet and let rest in refrigerator uncovered for 12 to 24 hours.

Step 5

Preheat oven to 300 degrees. Insert an oven probe thermometer into one of the tenderloins (if one is smaller in width test this one first, then after test for doneness of the second portion as the smallest will finish first).

Step 6

Transfer roast on the wire rack to a clean rimmed 18 by 13-inch baking sheet covered with aluminum foil. Sprinkle all sides with a fair amount of pepper (1 to 2 tsp total).

Step 7

Bake in oven until probe thermometer registers 125 degrees for medium-rare or 130 degrees for medium in center (this will take about 1 hour to 1 hour 40 minutes depending on thickness of the tenderloin you used and desired doneness). Test both portions.

Step 8

Remove tenderloins from oven and let rest 10 minutes.

Step 9

Preheat vegetable oil a cast iron skillet over medium-high heat.

Step 10

Dab exterior of each tenderloin dry with paper towels. Transfer both to skillet and sear about 1 to 2 minutes per all 4 sides until well browned. Once you turn to the 4th side add the butter, garlic, thyme and rosemary to the skillet around the tenderloins.

Step 11

Remove the tenderloins to a cutting board and let the butter cook in skillet 1 minute longer if it hasn't yet browned and the garlic isn't toasted. Then pour butter into a dish so it doesn't continue to cook and burn.

Step 12

Cut and remove twine. Slice tenderloins into 1/2-inch thick slices, then remove herbs from garlic butter and drizzle it over the beef. Season lightly with salt and pepper as desired.