In a skillet over medium heat, toast the guajillo and ancho peppers for about 2-3 minutes until fragrant. Remove from heat and soak the peppers in hot water for 15 minutes until softened. Drain and set aside.

In a blender, combine the soaked peppers, onion, garlic, cumin, oregano, smoked paprika, salt, black pepper, beef broth, and apple cider vinegar. Blend until smooth.

Place the beef chuck roast and short ribs in the Instant Pot. Pour the blended sauce over the meat, ensuring it is well coated.

Close the lid of the Instant Pot and set it to cook on high pressure for 45 minutes. Allow for a natural release for 15 minutes before manually releasing any remaining pressure.

Remove the meat from the pot and shred it using two forks. Strain the remaining liquid to separate the fat and solids, reserving the broth for dipping.

Heat a skillet over medium heat. Dip a corn tortilla into the reserved broth, then place it in the skillet. Add a portion of the shredded meat and top with chopped onions and cilantro. Fold the tortilla in half and cook until crispy, about 2-3 minutes per side.

Repeat with remaining tortillas and filling. Serve the tacos hot with lime wedges and the reserved broth for dipping.