Dice your white onion and add to a saute pan. Cook for about 10 minutes or until they become light brown and transparent.
Combine oregano, thyme, cumin, salt, ancho chili and cloves. Pat your tenderloin dry with a paper towel and rub all over tenderloin.
Place the tenderloin in slow cooker and combine all ingredients including onion. Combine well.
Slow cook on low for 8-12 hours.
Once the tenderloin has finished, let it cool down so it's safe to touch. Set the liquid aside(don't toss it!). Shred tenderloin using a fork. The pieces will be long so you will want to give it a rough chop to cut them in half.
Once you have chopped all the pork a bit, heat up a large non stick pan and add your pork. Don't over crowd your pan. This should be done in several batches (3-4). Drizzle some of the juices over it and let it crisp up a little bit. This recipe isn't meant to be a crispy meat so don't let it get too crispy. We want it to remain juicy.
Once you are ready to serve, add meat to your tortilla and drizzle some juice over it. Best served with some raw chopped onion on top!