Make the marinade: Whisk all marinade ingredients together in a bowl until smooth. Reserve ¼ cup in a separate small bowl (this becomes the finishing sauce and must not touch raw pork).
Marinate: Pat pork dry with paper towels. Season lightly with salt and pepper. Coat generously with the remaining marinade. Place in a zip-lock bag or covered dish and refrigerate for at least 30 minutes, up to overnight. Longer = better flavor.
Preheat oven to 400°F (200°C). Position rack in center.
Pat dry: Remove pork from marinade. Pat the surface thoroughly dry with paper towels — this is essential for a proper sear.
Sear: Heat olive oil in a large oven-safe cast iron or stainless steel skillet over medium-high heat until shimmering. Add pork and sear 2–3 minutes per side without moving, turning to brown all sides (about 8–10 minutes total). The pan should be hot enough that the meat sizzles assertively on contact.
Roast: Transfer skillet to oven. Roast 14–18 minutes, flipping halfway, until an instant-read thermometer inserted into the thickest part reads 145°F. Start checking at 12 minutes.
Rest: Transfer pork to a cutting board. Tent loosely with foil and rest 5–10 minutes. Do not skip this step.
Sauce: Pour the reserved marinade into the hot skillet and heat over medium for 1–2 minutes, scraping up any browned bits, until slightly thickened. (Optional: stir in 1 tbsp cold butter off the heat for a glossier sauce.)
Slice into ½-inch diagonal medallions. Drizzle with the pan sauce.
