Discard excess water from the soaked lentils. Add 2 cups of fresh water and 1/2 tsp turmeric powder and cook it in a pressure cooker until it turns mushy.
While the lentils cook, heat oil in a pan. Add cumin seeds and fry them for a few seconds on medium heat.
Add shallots, garlic and green chillies. Fry them till the shallots turn translucent.
Add pumpkin cubes and thinly sliced tomato.
Add salt, 1/2 tsp turmeric powder and sambar powder.
Reduce the heat. Cover the pan with a lid and cook till the tomato turns mushy and the pumpkin is cooked (but still has a bite).
Then, add cooked lentils.
Add tamarind juice and jaggery. Taste and adjust the salt.
Bring it to a boil.
While the sambar boils, prepare the tempering by frying cumin/mustard seeds, curry leaves, dry red chillies and asafoetida on medium heat.
Add this to the boiling sambar. Garnish with finely chopped fresh coriander leaves.
Serve hot with steamed rice and ghee.