Preheat your oven to 225°F (107°C). Line a baking sheet with foil and place a wire rack on top.
Pat the tenderloin dry with paper towels. Season generously with salt and freshly ground black pepper, ensuring an even coating on all sides.
Place the tenderloin on the prepared rack. Insert a meat thermometer into the thickest part of the meat.
Roast in the oven until the internal temperature reaches 10–15°F below your desired doneness. This usually takes about 30 minutes per pound.
Medium-rare: 120–125°F
Medium: 130–135°F
This will take approximately 60–90 minutes, depending on the size of your tenderloin.
Remove the tenderloin from the oven and let it rest for 10–15 minutes. Cover loosely with foil while you prepare for searing.
Heat a large cast-iron skillet over high heat. Add the oil and allow it to shimmer.
Sear the tenderloin for 1–2 minutes on each side, including the ends, until a deep, golden-brown crust forms.
Reduce the heat slightly and add the butter, minced garlic, rosemary, and thyme to the skillet.
Spoon the melted butter and aromatics over the tenderloin as it sears to infuse flavor.
Remove the tenderloin from the skillet and let it rest for 5–10 minutes to allow the juices to settle.
Slice into ½-inch to 1-inch medallions and serve warm.