Mix the spice rub: In a small bowl, combine salt, pepper, smoked paprika, cumin, chili powder, garlic powder, onion powder, and brown sugar.
Prep the pork: Pat the pork shoulder dry with paper towels. Rub the spice mix all over, pressing it into the meat on all sides.
Optional sear for more flavor: Heat oil in a large skillet over medium-high.
Sear the pork 2–3 minutes per side until deeply browned. This step adds richness but isn’t required if you’re short on time.
Build the crockpot base: Add sliced onion and smashed garlic to the slow cooker. In a separate bowl, whisk orange juice, lime juice, broth, tomato paste (or salsa), and vinegar until smooth.
Pour over the onions.
Cook low and slow: Place the pork in the crockpot. Cover and cook on Low for 8–10 hours or High for 4–6 hours, until the pork is fork-tender and easily shreds.
Shred and moisten: Transfer the pork to a cutting board. Skim excess fat from the cooking liquid.
Shred the pork with two forks, then return it to the slow cooker and toss with enough juices to keep it moist but not soupy.
Adjust seasoning: Taste and add a pinch of salt, extra lime juice, or a splash of vinegar if it needs more brightness.
Warm the tortillas: Toast corn tortillas in a dry skillet 20–30 seconds per side or wrap a stack in a damp paper towel and microwave until pliable. Keep warm in a towel-lined basket.
Assemble tacos: Fill each tortilla with pork and top with your favorites—onion, cilantro, cabbage, cotija, pickled onions, salsa, and a squeeze of lime.
Optional crispy finish: For carnitas-style edges, spread some shredded pork on a sheet pan, drizzle with a bit of cooking liquid, and broil for 3–5 minutes until browned and crisp at the tips.