Pressure cook the dal with 1/2 teaspoon turmeric powder and about 3 cups of water.
When the dal is cooked, open the pressure cooker, mash well and add salt, tomatoes, white pumpkin/ash gourd, tamarind juice, coriander powder and chilli powder and simmer for a few more minutes till the white pumpkin is cooked.
Add some more water if required and turn off flame.
In another vessel, heat oil and add mustard seeds, broken red chillies and curry leaves.
When the mustard splutters, add the cooked dhal and vegetable.