Add all ingredients for the sauce to a large (6-quart) slow cooker and stir well.
Sprinkle the beef chuck roast with garlic powder and sea salt. Heat the oil to medium-high in a thick-bottomed stock pot or Dutch oven. Place the meat inside the hot stock pot and sear for 4 to 5 minutes, until the outside is deeply browned. Carefully flip the meat and sear the other side for 2 to 3 minutes. Note: you can use a cast iron skillet, but proceed with caution, as the fat from the beef will splatter out.
Transfer the meat to the crock pot and nestle it in the sauce. Note: it’s fine if the meat isn’t fully submerged in sauce!
Secure the lid on the slow cooker and set on the lowest setting. Cook 6 to 8 hours, flipping the meat halfway through, if possible, or until beef is very tender.
Transfer the beef to a cutting board and use two forks to shred it. Transfer the shredded beef back into the crock pot with the sauce and stir well so the meat absorbs the flavor of the sauce.
Preheat the oven to 400 degrees. Spread the potatoes on a large baking sheet and drizzle with 2 Tbsp avocado oil. Use your hands to toss everything together until potatoes are well-coated. Sprinkle with sea salt and place on the center rack of the preheated oven. Roast 20 minutes, stir the potatoes, then roast an additional 10 to 15 minutes, until golden-brown and cooked through.
While the potatoes are roasting, fry the plantains. To do so, fill a small shallow skillet half-way up with avocado oil and heat over medium-high. Once the oil is all the way hot (you can test this by gently flicking a tiny amount of water on the oil to see if it sizzles), carefully place sliced plantains in the oil. Cook until golden-brown and crispy, about 2 to 3 minutes. Carefully flip and cook on the other side an additional 2 to 3 minutes, until plantains have reached desired level of crisp. Transfer to a paper towel–lined plate, sprinkle with sea salt, and repeat for remaining plantains.
Place sliced red cabbage in a mixing bowl and add the lime juice. Firmly massage the lime juice into the red cabbage until it begins to soften, about 2 minutes. Sprinkle with sea salt to taste.
Divide potatoes between 4 to 6 bowls and add desired amount of shredded beef and cabbage. Serve with fried plantains, tomatoes, and fresh cilantro.