Combine Kosher salt, cumin, chili powder, oregano, garlic powder, onion powder, and black pepper in a small bowl, then whisk well. Season the pork shoulder pieces on all sides.
Heat a large pot over high heat, then add avocado oil. When very hot, add half of the pork at one time, searing until golden brown on all sides. Transfer to a large plate, then repeat with remaining pork and set aside. Do not drain the drippings.
Add thinly sliced onion to the hot pan, then scrape up all the brown bits. This equals flavor! Cook until softened, about 3-5 minutes.
Return the seared pork to the pot, then add chicken stock or beer. Add the zest and juice of orange and limes. Bring to a boil, then reduce the temperature to a simmer. Cook until the pork is fall apart tender. Keep an eye on the liquid!
Transfer the pork carefully to a large mixing bowl or tray and allow to cool until you're able to handle the meat. Pull or shred the pork. We like to press lightly on it with a fork.
You can either return the pulled pork to the pot along with the drippings and the onion and serve it straight from there, or transfer to a parchment-lined rimmed baking sheet, then heat under a broiler on high.
Serve the pork in tacos that have been warmed with chopped onion, fresh cilantro, and lime wedges.