Measure out all the ingredients and keep them separate (especially the spices, they are added at different times during cooking).
Heat the coconut oil in a large pot over medium-high heat and add the mustard seeds.
Cover the pan once they begin to pop and reduce the heat to medium. When a good portion of the mustard seeds have popped and turned grey add the urad dal, cumin seeds, cinnamon stick and fenugreek. Toast until fragrant.
Next add the curry leaves, chilies and ginger and stir to continue toasting (Add fresh turmeric here if you are using it instead of dried powder).
Add turmeric (powder) and coriander, stir well and toast for a few seconds. Add the onion and cook until softened, adding a touch of water if needed to prevent the spices from sticking.
Add the tomatoes and salt and bring to a boil. Reduce the heat to a simmer and cook until the tomatoes are beginning to break down.
Take the pot off the heat and finish with the citrus juice and cilantro.
Taste and adjust the seasoning of the sauce and add the roasted cauliflower and squash.
Cook to heat through, a couple of minutes. Stir in the optional green vegetables at the end and cook with the residual heat just until wilted.