01 - In a small bowl, combine the ground cumin, dried oregano, smoked paprika, sea salt, black pepper, and cinnamon. Mix thoroughly until evenly incorporated.
02 - Place the beef chuck chunks into the slow cooker. Sprinkle the spice blend evenly over the meat and toss to coat all sides thoroughly.
03 - Add the chopped onion, minced garlic, chopped chipotle peppers, and jalapeño to the slow cooker, distributing them around and over the seasoned beef.
04 - In a separate bowl, whisk together the fresh lime juice, apple cider vinegar, beef broth, and tomato paste until smooth. Pour the mixture evenly over the beef and vegetables.
05 - Tuck the bay leaves into the liquid around the beef to infuse flavor during cooking.
06 - Cover the slow cooker and cook on LOW for 8 hours, or until the beef is fork-tender and shreds apart effortlessly.
07 - Remove and discard the bay leaves. Using two forks, shred the beef directly in the slow cooker, mixing it well with the accumulated cooking juices.
08 - Serve the barbacoa hot in tacos, burritos, or over rice, accompanied by your favorite toppings such as cilantro, diced onion, and lime wedges.