Remove the stems and seeds from the dried ancho and guajillo chiles. Add the beef stock to a medium-sized pot and bring to a boil. Add chiles, turn off the heat, cover, and let sit for 15-20 minutes.

When the peppers are softened, add them to a blender or food processor along with the remaining ingredients and blend until smooth. Adjust with more beef stock or water for desired consistency if needed.

Preheat the oven to 350 degrees Fahrenheit. In a Dutch oven over medium-high heat, add olive oil. Sear the chopped beef chunks for 3-4 minutes on each side, seasoning with salt, black pepper, and garlic powder. Remove seared meat from pot.

In the same pot, add the onions and saut? until fragrant and translucent, about 1-2 minutes. Stir in the chili paste and simmer for 1-2 minutes. Add the beef stock and water, then add the seared beef.

Carefully transfer the Dutch oven into the oven and braise for about 2 ? hours, or until the beef is tender and easily shredded.

Remove from oven and shred the meat until it has a pulled texture. Reserve 1 cup of the broth in a small bowl and top with chopped cilantro for the dipping sauce.

In a medium skillet over medium heat, add olive oil. Dip a tortilla in the dipping sauce, place it in the skillet, and fry for a few seconds. Top with shredded beef, diced onions, and cheese. Flip in half and allow the cheese to melt, then flip again for a nice char. Remove from heat when golden and repeat until all tacos are made.

Serve with the dipping sauce, Pico de Gallo, or other preferred sides.