To make the carnitas, place the pork shoulder, halved orange, quartered onion, smashed garlic, bay leaves, sea salt and water in a large, heavy-based casserole or lidded saucepan. Bring to the boil over high heat.
Turn the heat down to low, cover and simmer gently for 2½ to 3 hours, until the pork is very tender. Remove about 120 ml of the cooking liquid and use two forks to shred the pork.
Heat 1 tbsp of the reserved cooking liquid (or a little oil) in a frying pan over medium-high heat. Add the shredded pork and fry, stirring occasionally, until golden and crispy. Transfer to a bowl and set aside.
For the salsa roja, put the plum tomatoes and dried arbol chillies in a saucepan and cover with water. Bring to the boil, then simmer for 10 to 15 minutes, until the tomatoes have softened and the chillies have rehydrated. Drain, reserving about 120 ml of the liquid.
Blend the tomatoes, chillies, garlic, the quarter of a small white onion, ground cumin, dried oregano, chicken stock and sea salt until completely smooth, adding a little of the reserved liquid if needed. Pour into a saucepan and simmer over a low heat for 10 to 15 minutes, stirring occasionally. Keep warm.
For the salsa picante, blend the habanero chillies with the distilled white vinegar and sea salt until smooth. Handle with care and start with just a few drops when serving.
To assemble, warm the rolls if you like, then spread the refried beans on both cut sides. Pile the crispy carnitas on the bottom halves, then fully dip each sandwich into the warm salsa roja so it’s soaked through.
Serve the tortas ahogadas immediately. Drizzle with salsa picante, top with pickled red onions and have plenty of napkins to hand.