Preheat the oven to 180C/350F/gas 4.
Heat the oil in a casserole dish over a medium heat. When the oil is hot, add the cumin and fry until it sizzles. Add the star anise, cardamoms and peppercorns and fry until aromatic, but not much longer than a minute in case they burn.
Stir in the onion, garlic, chilli and ginger, reduce the heat to low and cook gently for 10 minutes then stir in the orange zest. Cook for a further 10-15 minutes, or until the onions are softened and caramelised.
Add the tomato purÃ©e and fry for 2-3 minutes then stir in the ground turmeric, garam masala and ground coriander. Season with salt and freshly ground black pepper and fry for 2-3 minutes until aromatic. Increase the heat to medium and add the oxtail pieces. fry for 2-3 minutes, turning once or twice, or until lightly browned on all sides.
Pour in the passata and bring to a simmer then pour in just enough boiling water to almost cover the oxtail and tuck in the bay leaf. Stir then cover the casserole and transfer to the oven for one hour. Stir in the orange juice then return to the oven for a further 1-2 hours, or until the oxtail is almost falling off the bone.
Pull the meat off the bones and discard the bones. Garnish the curry with the fresh coriander and sprinkle with a couple of teaspoons of garam masala and serve.
For the pink grapefruit chutney, mix all of the chutney ingredients together and season with salt and freshly ground black pepper. Transfer to a serving bowl.
Serve the oxtail curry with the pink grapefruit chutney and basmati rice on the side.