If needed, trim the 1,200g of pork and slice or pound it into thin steaks about 8–10 mm thick, using boneless shoulder steaks, pork neck, or loin pounded thin. In a large bowl, combine the 2 tsp kosher salt, 1 tsp black pepper, 1 tsp dried Mexican oregano, 4 finely grated garlic cloves, 120ml sour orange juice (or 80ml orange juice, 30ml lime juice, and 10ml grapefruit juice), 1 tbsp white vinegar, and 1 tbsp neutral oil. Add the pork, turn until every piece is coated, cover, and refrigerate for 2–4 hours. Do not marinate overnight. That limit is what keeps the pork tender, since strong citrus left too long turns the outside mealy and cured.

Put the 2 thinly sliced medium red onions in a bowl and add 180ml sour orange juice (or 120ml orange juice, 45ml lime juice, and 15ml white vinegar), ½ tsp kosher salt, ½ tsp sugar, ¼ tsp dried Mexican oregano, and the optional habanero. Toss well and let stand for at least 30 minutes while the pork marinates, tossing once or twice. The onions should soften slightly and turn vivid pink while keeping a little bite. Keep them chilled until serving. That quick acid cure is what gives the plate a bright, refreshing counterpoint to rich grilled pork.

Heat 2 tbsp neutral oil or lard in a saucepan over medium heat. Cook the ½ small finely diced white onion for 3–4 minutes until softened, then add the 2 minced garlic cloves and cook for 30 seconds. Add the 2 drained cans of black beans, the reserved 180ml bean liquid or water, 1 bay leaf, and ½ tsp ground cumin, then simmer for 10–15 minutes, stirring occasionally, until hot and lightly thickened. Mash some of the beans lightly, keeping most whole, season with ½–1 tsp kosher salt and black pepper, and remove the bay leaf. The beans should be spoonable, not soupy. That thickness is what lets them sit neatly on the plate as a side rather than a stew.

Preheat a grill or grill pan to high heat, so the cooking surface is very hot before any pork goes on, and lightly oil the grates if needed. Lift the pork out of the marinade, let the excess drip off, and discard the used marinade. Do not grill the pork dripping wet. A scorching surface and a surface-dry steak matter equally. That combination is what lets the meat sear and char on contact instead of steaming in its own liquid.

Grill the pork in batches without crowding, cooking about 2–3 minutes on the first side and 1–2 minutes on the second, depending on thickness, until the steaks show dark char marks and lightly crisp edges. Target a centre temperature of about 63–68°C, just cooked through, and avoid going further, because thin pork dries very fast. On a grill pan, empty any accumulated liquid between batches. Rest the pork for 5 minutes, and while it rests, place the 2–3 halved oranges cut-side down on the grill until well charred and lightly caramelised. That short rest is what lets the juices settle back into the meat before serving.

Divide the pork between 4 plates, about 300g of raw marinated pork per serving, arranging the steaks in overlapping pieces. Add a mound of the pickled red onions and a portion of black beans beside the pork, then place the charred citrus halves on each plate. Scatter a small handful of fresh cilantro leaves over the top and offer extra lime wedges if you like. Serve immediately, squeezing the charred citrus over the pork at the table. That immediate serving is what keeps the pork smoky and juicy, with the char still crisp against the cold, sharp onions.