Tie the tenderloin tail to have a consistent size from end to end.
Combine soy sauce, ginger, orange zest, garlic, and pepper. Slowly whisk in sesame oil.
Place the pork in a large zip lock baggie or a shallow pan (covered in plastic wrap). Cover the tenderloin with the marinade, ensuring to coat evenly. Refrigerate 2-3 hours or overnight.
Preheat oven to 425 degrees. Heat a large oven proof sauté pan over medium heat. Add a thin coat of coconut oil. Sear the tenderloin on both sides for 3-4 minutes. Baste with leftover marinade. Put the tenderloin in the oven for 10-15 minutes or until it reaches an internal temperature of 145 degrees. Let rest for 10 minutes then slice and serve.