Using a peeler, remove just the ridges off the ridge gourd. It will peel off in ribbon like bits. Leave the rest of the skin on. Chop the ridge gourd into small-ish pieces. You don’t need to remove the central part/ core of the vegetable, if it is tender.
Heat the 1/2 tsp of oil and pan sauté the sliced onion until it is soft and starts caramelizing. Remove and keep aside. In another 1/2 tsp of oil, sauté the ridge gourd pieces over medium heat until they’re soft and cooked. Let it cool.
In the last remaining 1/2 tsp of oil, sauté the lentils till golden brown. Stir in the asafoetida and dried red chillies and take off the heat. Stir in the curry leaves and transfer all this to your blender jar.
Add the tamarind, the sautéed onions and ridge gourd pieces to the blender with salt. Grind/ Blend till smooth. Transfer to a serving bowl and drizzle with a little more coconut oi, if using. Serve with rice and molagootal, or chappathis, or dosa.