Season the beef chunks with salt, black pepper, cumin, oregano, smoked paprika, garlic powder, onion powder, and cayenne pepper. Rub the spices into the meat thoroughly.

Place the seasoned beef in the slow cooker. Add the apple cider vinegar, lime juice, beef broth, and bay leaves.

Cover and cook on low for 8 hours or high for 4 hours, until the beef is tender and easily shredded.

Once cooked, remove the beef from the slow cooker and shred it using two forks. Discard the bay leaves.

Return the shredded beef to the slow cooker and stir to combine with the juices. Let it sit for an additional 10-15 minutes to absorb the flavors.

Warm the tortillas in a skillet or microwave. Serve the shredded barbacoa beef in tortillas, topped with fresh cilantro, diced onions, and lime wedges.