Preheat oven to 200°C. Line an oven tray or roasting dish with baking paper.
Place orange juice, honey, star anise, chilli, sesame oil, soy sauce and tamarind purée in a small pot. Bring to boil and cook on medium-high heat until syrupy and reduced to about ½ cup liquid (about 12-15 minutes). Reserve about one-third of the glaze in a ramekin for serving.
Heat olive oil in a large frying pan on a high heat. Season lamb with salt and sear in frying pan for about 2 minutes on each side. Transfer to oven tray and spoon over glaze, reserving a little for basting. Roast for about 30 minutes for medium lamb, basting once with glaze halfway through.
Cover lamb with foil and rest for about 15 minutes before slicing. Spoon over reserved glaze and scatter with coriander. Serve with steamed bok choy and rice or roast pumpkin, potatoes or kumara.
*Check label if eating gluten free.