2 guajillo chiles
2 tablespoons apple cider vinegar
1 teaspoon salt
2 cloves garlic
1/2 teaspoon dried oregano
1/4 teaspoon ground cumin
1/4 teaspoon ground coriander
dash ground cloves or allspice
1 pork tenderloin (1–2 pounds)
1 tablespoon vegetable oil
Toast the dried chiles on a dry skillet over medium-high heat for several seconds on each side until pliable. Break off the stem and shake out the seeds. Rinse them off. Cover the chiles with 1 cup very hot water and set aside for at least 30 minutes. You will use some of the soaking water in the marinade so don’t toss it!
Peel garlic cloves and toss into blender with vinegar, salt, spices. Add the soaked chiles and 1/4 cup of the chile-soaking water. Blend until smooth. (Marinade can be refrigerated in a jar for a couple days.)
Coat the tenderloin in this sauce and refrigerate 6-10 hours.
When ready to cook, preheat oven to 425ºF.
Heat a cast iron skillet (or other heavy, oven-safe skillet) over high until very hot. Add the oil. Pull the pork from the marinade (reserve it though!) and place in the hot pan. Let cook 3 minutes. Turn and brown the other side for 3 minutes.
Transfer skillet to oven and roast 10-15 minutes, until the internal temperature reaches 155ºF.
While it cooks, add about 1/4 cup water to the remaining marinade and bring to boil in a small pot. Let it boil a few minutes.
Let pork rest for 5-10 minutes before slicing and serving with boiled marinade.