In a large pot, heat a little oil over medium heat. Add the beef chuck roast and short ribs, browning on all sides. Remove from the pot and set aside.

In the same pot, add the quartered onion and minced garlic. Sauté until the onion is translucent.

In a small bowl, soak the guajillo and ancho peppers in hot water for about 15 minutes until softened. Drain and blend them with cumin, oregano, paprika, salt, black pepper, beef broth, and apple cider vinegar until smooth.

Pour the blended sauce into the pot with the sautéed onion and garlic. Add the browned beef back into the pot. Bring to a simmer, cover, and cook on low heat for about 2-3 hours, or until the meat is tender and easily shredded.

Once cooked, remove the meat and shred it using two forks. Strain the broth and set aside.

Heat a skillet over medium heat. Dip each corn tortilla in the reserved broth, then place it in the skillet. Add a portion of the shredded meat and fold the tortilla in half. Cook until crispy, about 2-3 minutes per side.

Serve the tacos with chopped cilantro, diced onion, and lime wedges on the side.