Add the chopped onion to the crock pot. Sprinkle the meat with cumin, paprika, coriander, garlic powder, and sea salt and gently rub into the meat with your hands. Place the meat in the crock pot and add the beer and lime juice. Secure the lid and cook 8 to 12 hours on low.
Transfer the meat to a cutting board and use two forks to shred it. Place the meat back into the crock pot to allow it to soak up the juices.
When you're ready to prepare the tacos, heat a large cast iron skillet (I use a 12-inch) to medium-high. Add the chorizo and cook until meat is cooked through and the majority of the juices have burned off.
Using a slotted spoon (to strain the juices), transfer the shredded pork to the skillet and continue cooking until meat has a nice crisp to it and juices have burned off (note: this may need to be done in batches depending on the size of your skillet. If you aren't making a ton of tacos all at once, you can do this step with only part of the chorizo and part of the pork, saving the rest for later).
Heat up your favorite tortillas using your preferred method (microwave, oven, or stove top).
Load up the tortillas with the carnitas/chorizo mixture and top with chopped onion, tomato, and cilantro. Devour!
*Omit onion and garlic powder to make Low-FODMAP
**Go for a light beer, such as Corona or 805 - don't use anything too hoppy. Omit beer to make gluten-free (you won't need to replace it with anything else).
***I use Diestel Turkey Chorizo which is much leaner than pork chorizo and still absolutely delicious. Feel free to use your favorite chorizo.