Preheat a large skillet to medium-high heat with olive oil. Pour half the beer and all of the tomato sauce into the bottom of a slow cooker.

Combine all the spices together and rub them all over the meat. When the skillet is very hot (preheat for 7-10 minutes), add the roast and sear on all sides until brown and crusty, about 5 minutes per side.

When the roast is brown all over, move it to the slow cooker. Turn the heat off the skillet. Add the rest of the beer and swirl to deglaze, then pour the beer and drippings into the slow cooker.

Cook the beef on low for 8-10 hours (I do this overnight), then remove the beef to a plate and the drippings to a small skillet. Shred the beef with forks, removing any large fatty pieces. Heat the drippings over medium heat and let them simmer and reduce for about 15 minutes.

To serve, return the beef to the slow cooker on Low or Warm. Drizzle with some of the drippings, then taste the meat and add salt if needed - mine needed about a teaspoon extra.

Serve the beef with your favorite Mexican meal with extra drippings for dunking and drizzling. Enjoy!