Remove stems and seeds from the guajillo and ancho chiles. Toast them in a dry skillet over medium heat for about 2-3 minutes until fragrant. Then, soak them in hot water for 15 minutes.

Blend the Marinade

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

Marinate the Beef

Cut the beef chuck roast into large chunks. Place the beef in a large bowl, pour the blended marinade over it, and let it marinate for at least 2 hours or overnight in the refrigerator.

Cook the Beef

In a large pot, add the marinated beef along with bay leaves and beef broth. Bring to a boil, then reduce the heat to low, cover, and simmer for about 3 hours until the beef is tender.

Shred the Beef

Once the beef is cooked, remove it from the pot and shred it using two forks. Strain the broth and reserve it for serving.

Prepare the Tacos

Heat a skillet over medium heat. Dip each corn tortilla in the reserved broth, then place it in the skillet. Add shredded beef, diced onions, and cilantro. Fold the tortilla and cook until crispy on both sides.

Serve

Serve the tacos with lime wedges, additional diced onions, cilantro, and sour cream on the side.