Start by removing the stems and seeds from the dried guajillo and ancho peppers. Place them in a saucepan along with the beef broth. Allow the mixture to simmer for about 15-20 minutes.

After the peppers have softened, transfer them to a blender, including the broth from the saucepan. Add the chopped onion, minced garlic, apple cider vinegar, ground cumin, dried oregano, smoked paprika, salt, and pepper. Blend everything until smooth.

Place the beef chuck roast into your slow cooker. Pour the smooth pepper sauce over the beef, ensuring it's well-coated.

Set your slow cooker to low and cook for about eight hours.

Once the cooking time is up, use two forks to shred the meat in the slow cooker and mix it with the sauce.

Warm the corn tortillas in a skillet over medium heat.

Fill each tortilla with a generous helping of the shredded beef and top with chopped onions and cilantro.

Serve with reserved broth for dipping if desired.