I modified this recipe from one on Chef Mommy. I didn't make many changes, but the ones I did are important. First off, I omitted the Worcestershire Sauce because it has anchovy paste in it, and I am allergic to fish. Without it, the recipe does not suffer.
1/2 cup olive oil
1/3 cup soy sauce (or coconut aminos if you don't do soy)
1/4 cup red wine vinegar
juice and zest of one lemon
4 tbsp chopped cilantro
1 tbsp dry mustard
1 tsp black pepper
3 garlic cloves, minced
1 lb pork tenderloin (I bought an organic tenderloin, and the quality difference was noticeable.)
Combine all the ingredients in a gallon sized plastic bag and marinate in the refrigerator for at least 3 hours. I took it out at the three hour mark and it turned out very well.
Preheat the oven to 350 degrees. In a large cast iron skillet over medium high heat, sear two sides of the tenderloin for three minutes each side. Place the whole pan in the oven and cook for 30 minutes or until the internal temperature is 160 degrees. Remove from the oven and flip the tenderloin. Let sit about ten minutes before slicing thin. I served this roast with new potatoes with ginger and mint, and crispy cauliflower. Both recipes to come. Enjoy!