Prep the pork: Pat the tenderloins dry with paper towels and trim any silver skin.
Season lightly with salt and black pepper on all sides.
Make the marinade: In a bowl, whisk together soy sauce, honey (or maple), brown sugar, apple cider vinegar, garlic, ginger, Dijon, black pepper, and red pepper flakes. Reserve 1/3 cup for glazing later.
Marinate briefly: Place pork in a zip-top bag or shallow dish and pour the remaining marinade over it. Let it sit for 20–30 minutes at room temperature, or refrigerate up to 4 hours.
If marinating longer than 30 minutes, bring to room temperature for 20 minutes before cooking.
Preheat and sear: Heat oven to 400°F (200°C). In an oven-safe skillet, heat 1 tablespoon olive oil over medium-high. Sear pork for 2–3 minutes per side until nicely browned.
Roast: Transfer skillet to the oven.
Roast 12–18 minutes, turning once and brushing with some of the reserved glaze halfway through. Cook until the thickest part reaches 140–145°F (60–63°C).
Rest the meat: Move pork to a cutting board and tent loosely with foil. Rest for 5–10 minutes so the juices redistribute.
Make the glaze (optional but great): While the pork rests, pour the pan juices into a small saucepan.
Add the remaining reserved glaze. If you want it thicker, mix cornstarch and water into a slurry and whisk it in. Simmer 2–3 minutes until glossy and slightly thickened.
Slice and serve: Slice pork into 1/2-inch medallions.
Spoon glaze over the top. Finish with chopped parsley or green onions, and a little citrus zest if you like.