01 - In a small mixing bowl, combine ground cumin, dried oregano, smoked paprika, sea salt, black pepper, and cinnamon. Stir until evenly incorporated.
02 - Arrange the beef chuck chunks in the slow cooker insert. Sprinkle the spice blend generously over the meat and toss by hand until every piece is thoroughly and evenly coated.
03 - Scatter the chopped onion, minced garlic, chipotle peppers, and jalapeño over and around the seasoned beef pieces.
04 - In a separate bowl, whisk together the fresh lime juice, apple cider vinegar, beef broth, and tomato paste until smooth. Pour the liquid evenly over the beef and aromatics in the slow cooker.
05 - Tuck the bay leaves into the liquid around the beef so they remain submerged during cooking.
06 - Secure the lid on the slow cooker and cook on the LOW setting for 8 hours. The beef is ready when it pulls apart effortlessly with gentle pressure from a fork.
07 - Discard the bay leaves. Using two forks, shred the beef directly in the slow cooker, allowing the meat to absorb the rich cooking juices. Toss everything together until well combined.
08 - Serve the barbacoa hot in warm corn or flour tortillas, burritos, or over steamed rice. Garnish with fresh cilantro, diced white onion, and lime wedges as desired.