1. Fill and boil your kettle. Tip the lentils into a bowl, cover with cold water and set aside to soakl. Peel and finely chop the onion. Peel and grate the ginger and garlic. Heat a large pan and drizzle in 1 tbsp oil. Add the chopped onion with a pinch of salt. Fry for 10 mins, stirring often, till the onions are glossy and have browned.
2. While the onion cooks, coarsely grate the courgettes. Set aside in a colander to drain. Drain and rinse the lentils.
3. Add the ginger, garlic, 1 tbsp curry powder and 1 tbsp black mustard seeds to the pan. Cook for 2 mins, stirring, till the pan smells aromatic. Tip in the lentils and stir well. Crumble in the stock cube and pour in 500ml hot water from the kettle. Pop a lid on the pan and simmer the veg for 10 mins, stirring now and then.
4. Meanwhile, tip the flour into a large bowl, saving 1 tbsp for later. Add a pinch of salt. Add 1 tbsp oil and spoon in 2 tbsp yogurt. Add 2 tbsp cold water and mix together to form a smooth dough. Cover with a tea towel and leave to rest for 5-10 mins.
5. When the lentils have cooked for 10 mins, add in the grated courgettes. Pour in 200ml more hot water. Pop the lid back on and cook for a further 10 mins till the lentils are tender and thick. Finely grate the zest from the lemon. Thinly slice the spring onion, discarding the roots and any ragged greens. Set to one side.
6. Divide the dough into two balls. Dust your worktop with the 1 tbsp of reserved flour and roll the balls as thinly as possible. Rub each side of each flat bread with 1 tsp oil.
7. Heat a large frying pan for a couple of mins. When hot, carefully lay one flatbread in the pan. Cook for 2 mins then flip over and cook for 2 mins on the other side. Remove it from the pan and cover with a tea towel to keep warm. Repeat with the remaining flatbread.
8. Taste the dal and add a pinch more salt and pepper or a squeeze of lemon juice, if you think it needs it. Ladle the dal into warm bowls and top each one with a spoonful of yogurt, some sliced spring onions and lemon zest. Serve with the wamr flat breads on the side.