Heat the oil in a medium nonstick frying pan over medium heat.
Once shimmering, add the urad dal.
When it begins to turn golden, add the mustard seeds and dried red chilies.
As soon as the mustard seeds pop and the chilies darken—this will happen in seconds—add the chopped onion.
Stir and fry for 2 minutes.
Add the diced squash and continue to fry for another 4 minutes, stirring occasionally, until the squash and onions begin to caramelize at the edges.
Pour in 180 ml (6.1 fl oz) / ¾ cup of water and stir in the salt, brown sugar, ground cumin, and a generous grinding of black pepper.
Bring the mixture to a boil.
Reduce the heat to low, cover the pan, and simmer gently for about 10 minutes. The squash is ready when it's tender enough to be easily pierced with a knife.
Taste and adjust the seasoning if necessary. Just before serving, if there is any excess water in the pan, increase the heat to high and cook, stirring constantly, until the liquid has evaporated and glazes the squash.
Adjust the sweetness and heat to your liking. A little extra brown sugar can balance more chili, or vice versa.
