Preheat the oven to 180°C. Place the pork fillet in an ovenproof dish and, in a small bowl, stir together the passata, chilli powder, ground cumin, brown sugar, salt and garlic. Pour this mixture evenly over the pork, cover with foil and cook for between two and three hours, checking and turning if necessary half way through the cooking time..
To make the pickled red cabbage, heat the vinegar, salt and sugar over low heat and pour over the red cabbage. Let it cool before serving.
When cooked and super tender, shred the pork using two forks, pulling against the grain of the meat.