In a skillet over medium heat bring the beef, 2 1/2 cups of water, and 1 1/4 teaspoons of salt to a boil.
Reduce heat to low and cover for 1 hour and 45 minutes so that the beef becomes tender. Check the beef every thirty minutes and add water so that the bottom half of the beef is always submerged. When adding more water, flip the beef so that each side cooks evenly.
After 1 hour and 45 minutes, uncover the beef, increase the heat to medium, and simmer until the water evaporates and the beef begins to sizzle. This should take about 5-8 minutes.
Transfer the beef to a cutting board or baking sheet. Reserve the fat from the skillet and set aside. Next, wipe the skillet with paper towels.
Cover the beef with transparent deli sheets or foil. (I found that using the deli sheets was easier) Using a meat pounder, flatten the beef until it falls apart and begins to separate into shredded pieces.
Mix together the minced garlic, cumin, and vegetable oil in a small bowl. Combine the orange juice, lime juice, and lime zest in another bowl.
In the skillet, heat 1 1/2 teaspoons of reserved fat over medium heat. (Don't discard the rest of the fat) Add the sliced onion and a 1/4 teaspoon of salt. Saute until the onion is a golden and translucent. Next, add the white vinegar and stir the onions until the vinegar evaporates. Transfer the onions to a separate bowl, cover and keep warm.
Add the rest of the reserved fat and heat till it sizzles. Once the fat begins to sizzle add the beef and cook until a crispy crust forms on both sides. This should take about 2 minutes on each side. Reduce heat to low and gently push the beef to the outer edges of the skillet.
Add the garlic, vegetable oil, and cumin mixture to the middle of the skillet and cook for about 30 seconds.
Gently place the beef on top of the garlic mixture and flip the meat so that the mixture coats both sides. Take the skillet off of the heat and pour the juice and zest mixture on top of the beef.
Place the crispy shredded beef on a platter and put the sauteed onions on top. For another punch of flavor and freshness, squeeze lime juice over the dish and serve.