Halve the lemon and scoop out and discard the flesh. Finely chop the skin. Peel and remove seeds from the squash and cut flesh into 1cm (1/2in) dice. Heat 2tbsp of the oil in a large frying pan over a low heat. Add the squash and cook, stirring, for about 10 minutes. Add the onion and garlic and cook for a further 7-8 minutes, or until the vegetables are tender. Cook the couscous with the cinnamon stick in a large pot of boiling salted water, following pack instructions. Drain and add the couscous to the vegetables and toss with the remaining oil. Add the preserved lemon skin, lemon zest, chilli, parsley, mint, lettuce, pine nuts, raisins, allspice and salt and pepper to taste.
Toss to mix well and cook until heated through