Slice the pork tenderloin into very thin, bite-sized strips against the grain.
In a small bowl, whisk together the achiote paste, pineapple juice, apple cider vinegar, garlic powder, ground cumin, and dried oregano until the marinade is smooth.
Place the pork strips in a glass container, pour the marinade over them, and let them sit for at least 15 minutes.
Heat the avocado oil in a large skillet over medium-high heat until shimmering.
Add the marinated pork to the skillet and sauté for 5-6 minutes until the meat is cooked through and the edges are slightly caramelized.
Add the diced fresh pineapple and red onion to the skillet for the last 2 minutes of cooking to lightly char them.
In a separate pan, sauté the cauliflower rice over medium heat until tender and fragrant, then season with sea salt and black pepper.
Divide the cauliflower rice into bowls, top with the Al Pastor pork mixture, and garnish with fresh cilantro and a squeeze of lime juice.