Put the lentils, turmeric and 1.2 litres/2 pints water into a medium pan and bring to the boil. Cover partially and simmer gently for 20 minutes. Add the cayenne, beans, kale, coriander, carrot and salt. Stir and bring to the boil again. Cover partially and cook for another 20 minutes.

Meanwhile, make the curry paste: combine the ginger, garlic, ground cumin and coriander in a small bowl. Mix in 50 ml/2 fl oz water.

Pour the oil into a medium frying pan and set over a medium-high heat. When hot, add the whole cumin seeds. Let them sizzle for 5 seconds, then add the shallot. Stir and fry until lightly browned. Add the spice paste and fry until you can see the oil along the edges, about 1 1/2 minutes. Add the tomato passata and fry for about another minute, until you see the oil along the edges.

When the lentils have finished cooking, add the contents of the frying pan. Stir and cook gently for another 5 minutes.