Heat the oven to 180C/fan 160C/gas 4. Put the brown sugar into a medium frying pan over a low heat with 1 tbsp of water. As it melts, turn up the heat and keep shaking and swirling the pan until it forms a caramel the colour of a rusty penny. Add the pomegranate molasses and balsamic vinegar, and whisk well. Bubble for 2 minutes, then add the salt and chilli flakes. Put the whole pineapple in a roasting dish and pour over the caramel, ensuring it’s completely coated. Roast for 45-50 minutes, basting with the caramel a couple of times, until really tender to the point of a knife.