Wash and soak the lentils for atleast 30 minutes in 2 cups of water.You may also soak a combination of lentils such as moong dal,masoor,tuvar etc.
Boil the lentils along with chopped tomatoes , turmeric powder and salt in a pressure cooker. Pressure cook for 2-3 whistles.
Mash the lentils using a potato masher or mathni.
In a tadka pan, heat oil and add cumin seeds. Let it splutter. Add the ginger, chopped chillies and heeng. Mix well.
Add red chilli powder to the tempering and turn off the heat. Add the tempering to the boiled lentils.Let it simmer for few minutes.
You may garnish optionally with chopped coriander. Serve hot with rice or roti.