Heat a large non-stick frying pan over a medium heat. Add half of the ghee and cook pumpkin in batches, tossing the pan often until pumpkin is well coloured and starting to soften; set aside.
Add another tablespoon of the ghee, and working in batches, cook silverbeet until wilted and tender. Remove from pan and add to reserved pumpkin.
In the same pan, heat remaining ghee; add onions, garlic and ginger; cook until starting to soften and fragrant.
Add spices, stirring until fragrant. Add chillies, lentils and water. Bring to the boil; reduce heat to a simmer; cook, covered, stirring occasionally until dahl is thick and soupy, about 40 minutes.
Just before dahl is ready, heat vegetable oil in a large frying pan. Add cumin, mustard seeds and curry leaves; cook until the mustard seeds 'pop'.
Return pumpkin and spinach, with tomatoes and tempered spice mixture to pan with dahl; stir to combine and heat through. Season to taste and stir in half of the coriander, reserving the remainder for garnish.
Serve hot with basmati rice, chutney and cucumber salad.