Preheat oven to 450°F.
In a large bowl, combine all the ingredients except the pork tenderloin and orange juice.
Whisk together until thoroughly combined.
Add the pork tenderloin to the bowl and turn it over and over to coat all surfaces.
Cover and let it marinate at room temperature for about 1 hour, or place in the fridge to marinate overnight.
Take the pork out of the marinade when you are ready and place in a shallow baking dish.
Drizzle a little of the marinade over the tenderloins. Take the rest of the marinade, and strain out any solid bits. Set aside for now.
Roast in the oven for about 20 to 30 minutes, depending on thickness. A meat thermometer should read 145°.
Remove from the oven and let it rest for about 5 minutes before cutting.
While you wait, add the remaining marinade liquid and the orange juice (should be about 1/2 cup) to a small saucepan. Bring to a boil at a medium high setting. Let it boil, skimming off any foam, for about 10 minutes, or until it is reduce by up to 2/3.
Slice the pork tenderloin, and serve with the citrus sauce.