Pressure cook toor dal with enough water till it is soft and mushy. Meanwhile soak tamarind in 1/4 cup of warm water for about 10 minutes. Extract it's juice and keep it ready.
Next get the coconut puree ready. Grind coconut, cumin and green chillies together with little water to fine puree.
Heat a pan with oil, mustard seeds, lentils and curry leaves. Saute for a while and when the mustard seeds sizzle, add the chopped ridge gourd cubes. Saute and add turmeric and tamarind juice.
The ridge gourd which is soft veggie, takes very little time to cook. When the cubes turn little pale, add in cooked toor dal and coconut puree. Finally add salt and little water. Bring it to boil and switch off.
Tasty and delicious ridge gourd kootu is ready to serve with steamed rice.