In a large pot, combine the beef chuck roast, beef short ribs, quartered onion, minced garlic, guajillo peppers, ancho peppers, cumin, oregano, smoked paprika, salt, and black pepper. Pour in the beef broth and apple cider vinegar. Bring to a boil over medium-high heat.
Once boiling, reduce the heat to low, cover, and simmer for about 2 to 3 hours, or until the meat is tender and easily shredded with a fork. You can also use a slow cooker on low for 6 to 8 hours.
Remove the meat from the pot and shred it using two forks. Strain the broth to remove the solids and reserve the liquid.
Heat a skillet over medium heat. Dip each corn tortilla into the reserved broth, then place it in the skillet. Add a portion of shredded meat to one half of the tortilla, sprinkle with chopped cilantro and diced onion, and fold the tortilla over.
Cook for about 2 minutes on each side, or until the tortillas are crispy and golden brown. Repeat with the remaining tortillas and filling.
Serve the tacos hot with lime wedges on the side for squeezing over the top.