For the marinade, combine all the ingredients in a bowl then whisk them to form an emulsion. Add the beef making sure every piece is evenly coated. Cover and refrigerate.
Marinate the beef overnight in a bowl in the refrigerator. Before preparing, drain thoroughly and allow meat to come up to room temperature for about 30 minutes.
In a large soup pot, heat a few tablespoons of oil over medium-high heat until very hot. Sear the beef a few pieces at a time to develop a rich brown color on all sides as well as on the bottom of the pan. Do this in several batches if the pot is too crowded.
When all the beef is browned nicely and removed from the pan, add the onions, peppers, and garlic to the hot pan. Sauté for a few minutes then add the remaining ingredients to the pan along with the beef. Bring to a boil, scraping the browned bits off the bottom of the pan. Reduce heat to low, cover and simmer slowly for about 2 hours. The meat should be very tender and should easily fall apart when pricked with a fork.
Remove from heat, remove meat to a cutting board and shred with a pair of forks. Return to the pot and bring to a simmer, uncovered. Reduce the liquid until very thick, almost dry. At this point, adjust the seasoning with salt, pepper, and whatever additional heat you want to add if any.
Serve with tortillas, cheese, salsa, lettuce and guacamole for a great beef taco. Portion and freeze the remaining machaca in zip lock bags for later use.