You can use black, yellow, green, whatever lentils you like, but the important thing is you must first wash them well and leave them to soak in fresh water for an hour.
Cook the lentils with the turmeric and some salt in just enough water to cover until they are tender but not completely cooked and the water has evaporated.
Heat the oil in a karai or a saucepan, add the cumin seeds and fry until they crackle. Add the onions and sauté until golden brown.
Stir in the ginger and garlic purée and the chilli powder