Preheat the oven to 325 degrees F.
Sprinkle the chuck roast on all sides with a fair amount of salt. In a large Dutch oven or other heavy pot with a tight-fitting cover, heat the oil over medium-high heat. Add the roast and brown it on all sides, taking the time to get a nice crust on the outside. Remove the roast and set aside.
Add the onions and garlic cloves to the pot and cook until lightly browned, 3 to 4 minutes. Stir in the ancho powder, cumin and cayenne. Add the crushed tomatoes and the bay leaves, and stir. Return the roast to the pot and add the cilantro. Bring to a boil, then reduce the heat to a simmer. Cover with lid, place in the oven, and cook until the meat is fork tender, about 3 hours.
Carefully transfer the meat to a cutting board and shred with a knife. Pour the liquid into a blender and puree. Return the shredded meat to the pot, add the pureed liquid, and stir to combine. Add salt and pepper to taste.
To assemble: Lay some shredded beef on a tortilla, and top with guacamole and salsa. Garnish with cilantro leaves, sliced radishes and cotija cheese.
Pulse the tomatoes, garlic, red onions, serrano, lime juice, cilantro and some salt and pepper in a food processor. The mixture should be chunky. Add some reserved tomato juice if the salsa is too thick. Drizzle the salsa with olive oil, then cover with plastic wrap and set aside for 30 minutes to allow the flavors to marry.