Soak the guajillo and ancho chiles in hot water for about 20-30 minutes until soft.

In a blender, combine soaked chiles, garlic, onion, cumin, oregano, black pepper, and salt. Blend until smooth, adding a bit of the soaking water if necessary.

In a large bowl, toss the beef chunks with the blended marinade. Let it marinate for at least 1 hour, preferably overnight in the fridge for richer flavor.

In a large pot, add the marinated beef and pour in the beef broth. Bring it to a boil, then reduce to a simmer. Cover and cook for about 3 hours until the meat is tender and easily shreds.

Once cooked, remove the beef chunks from the pot and shred them using two forks. Set aside in a bowl.

Strain the cooking liquid to separate the solids. Return the liquid to the pot and reduce it slightly to intensify the flavors.

In a separate skillet, heat corn tortillas briefly until warm and pliable.

Fill each tortilla with shredded beef, adding diced onion and cilantro on top.

Serve the tacos with a bowl of the strained broth (consomé) for dipping.