Remove stems and seeds from the dried guajillo and ancho chilies, then toast them in a dry pan over medium heat for 2 minutes until fragrant.
Place the toasted chilies in a bowl of hot water to soak for 10 minutes until softened.
In a blender, combine the softened chilies, onion, garlic, cumin, oregano, cinnamon, and a splash of the bone broth; blend until a smooth paste forms.
Season the beef chuck roast with sea salt and black pepper.
Heat avocado oil in a heavy-bottomed pot or slow cooker insert over medium-high heat and sear the beef on all sides until deeply browned.
Pour the blended chili paste and the remaining beef bone broth over the meat.
Cover and cook on low for 6-8 hours (or high for 4 hours) until the beef is tender enough to shred easily with a fork.
Remove the beef, shred it with two forks, and return it to the pot to soak in the flavorful consommé.
Briefly dip each corn tortilla into the top layer of the consommé, then place on a hot skillet.
Fill the tortillas with the shredded beef, fold them over, and cook until slightly crisp on both sides.
Serve the tacos with a small bowl of the remaining consommé for dipping, garnished with fresh cilantro and a squeeze of lime.