Preheat the oven to 425°F. Combine squash with oil and salt; spread evenly on a baking sheet. Bake for 20~25 minutes or until lightly browned around the edges. Remove from the oven and set aside to cool.
While the squash is in the oven, cook the lentil/ dal until very soft and mushy.
Grind coconut along with sambar powder into a coarse paste. Add half of the roasted squash and grind to a smooth paste.
Heat ghee in a saucepan, add the mustard seeds and once they pop, add asafoetida/ hing and cook for few seconds. Add the curry leaves and scallion; saute till they turn soft.
Stir in the coconut paste, cooked lentils, reserved roasted squash, jaggery/ coconut sugar and salt. Simmer on medium flame, for 8~10 minutes until the flavors meld. Finally stir in the lemon juice and turn off the flame. Serve warm with rice and a curry.