Wash and soak Channa dal for about 2 hours (I soak all my dals including moong dal. Soaking dal helps removes the toxins from them and also makes them easy to digest)
Peel and chop tinda in four pieces. Keep aside.
In a pressure cooker, boil together dal, tinda, onion, green chillies and tomatoes. Add salt and turmeric along with it. This should take about one whistle and 6-7 minutes on simmer. Wait for the steam to escape.
Lightly pound together mustard seeds, fenugreek seeds (methi), fennel seed (sauf) and nigella seeds together/
Heat ghee in a tadka pan and add heeng to it. Let it sizzle and add the pounded spice mix. Saute for 2 minutes and add chilli powder and dry mango powder. Add the tadka to the dal and serve hot garnished with coriander.