1. In a bowl stir together the vinegar, sugar and nigella seeds with a pinch of salt until the sugar has dissolved. Add the cucumbers, stirring well, and leave to pickle for 15 mins, stirring occasionally. Drain off any excess liquid.
2. For the fritters, stir together the grated carrot, chopped chilli, red onion and beaten egg until evenly mixed. Season with plenty of black pepper and a pinch of salt, then add the ground cumin and flour. Mixed until combined and divide into 4.
3. Working in 2 batches, heat half of the oil in a large non-stick frying pan. Spoon half of the carrot mixture into 2 mounds in the pan and press to flatten. Fry for 3-4 mins on each side over a medium heat until browned and crisp. Lift out of the pan to drain on a plate lined with kitchen roll while you cook the rest of the mixture.
4. Heat the folded flatbreads according to pack instruction and spread each with 1 tsp of the chilli relish. Lay a couple leaves of lettuce on one side and top with a carrot fritter. Spoon the pickled cucumbers over the fritters before serving.
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