Place pork, miso paste, maple syrup, tomato sauce, chilli flakes, salt, pepper and broth in a pressure cooker or slow cooker. Pressure cook for 1½hours or slow cook for at least 6 hours. Shred with two forks.
Combine red onion and vinegar in a bowl and set aside to pickle.
Steam bao buns above boiling water for 7 minutes until fluffy.
Place pulled pork, carrot and pickled red onion in steamed bao buns.
Serve topped with coriander leaves, chilli flakes, sesame seeds, mayonnaise and lime juice.