In a large pot, heat the vegetable oil over medium-high heat. Add the beef chuck roast and short ribs, searing them on all sides until browned. Remove the meat and set aside.

In the same pot, add the chopped onion and garlic, cooking until softened, about 3-4 minutes.

In a blender, combine the guajillo and ancho peppers with 1 cup of beef broth. Blend until smooth.

Return the meat to the pot, then pour in the blended pepper mixture, remaining beef broth, apple cider vinegar, cumin, oregano, smoked paprika, salt, and black pepper. Stir to combine.

Bring the mixture to a boil, then reduce the heat to low. Cover and simmer for 2-3 hours, or until the meat is tender and easily shredded.

Once cooked, remove the meat from the pot and shred it with two forks. Strain the broth and reserve it for dipping.

Heat a skillet over medium heat. Lightly toast each corn tortilla for about 30 seconds on each side.

Assemble the tacos by placing a generous amount of shredded beef on each tortilla. Top with chopped cilantro and diced onion.

Serve with lime wedges and a small bowl of the reserved broth for dipping.