Heat oven to 200C/180C fan/gas 6. Mix the cinnamon and allspice together with 1 tbsp flaky sea salt. Lightly score the skin of the duck all over and rub with the spice mix. Put the duck on a rack, sit in a roomy roasting tin and roast for 25 mins. Remove the duck from the oven and reduce the temperature to 140C/120C fan/gas 1. Continue to cook for 1 hr 30 mins, basting every 30 mins. Turn the oven back up to 200C/180C fan/gas 6, brush the duck all over with the marmalade and return to the oven for 20 mins until the skin is beautifully glazed – if it’s still too lightly coloured, leave it in a little longer. Rest for 15-20 mins before serving.
While the duck is roasting, make the dressing. Heat the rapeseed oil in a small frying pan and fry the shallots until soft. Add the spices and fry for 1 min, pour in the olive oil and vanilla seeds and pods, gently warm to infuse for 20 mins, then add the raisins, vinegar and lime juice. Season and set aside to cool.
While the duck is resting, toss the quartered lettuces in the dressing. To serve, shred the meat from the bones and serve topped with lime zest alongside the salad.