Pressure-cook the red gram lentil in sufficient water until soft. Mash and keep aside.
Grind the coconut, cumin seeds and dry red chillies to a smooth paste, using very little water. Keep aside.
In a heavy bottomed pan, add the split yellow chick pea, cubed bottle gourd, 2 cups of water, salt and turmeric powder. Cook on low to medium heat until both the lentil and the bottle gourd are soft but not mushy.
Add the cooked red gram lentil and the paste and mix well. Simmer for a few minutes. Adjust the salt.
Heat oil in another pan and add the mustard seeds and split black gram lentil. When the mustard seeds start spluttering and the black gram lentil starts turning red, add the mixture to the cooked bottle gourd and mix well. Serve hot.