Make the kabocha cream sauce: Peel kabocha and chop into small pieces. Steam until fork tender (about 10 minutes on the stove, 5 minutes in the microwave). You can also steam the cashews with the kabocha to soften them. Add kabocha, cashews, and water to a blender and blend until smooth. Set aside.
Mix spices: Add all the spices to a small bowl and mix. Set aside.
Saute onion, celery, and carrots: Heat oil in a large pot over medium high heat. Add onion, celery, carrots, and a pinch of salt and cook until onions turn translucent (3-5 minutes).
Add garlic and ginger: Add garlic and ginger and stir until fragrant, 30-60 seconds.
Add spices: Add the spices and stir for 30 seconds.
Add tomatoes: Stir in tomatoes. Add a splash of water if needed to deglaze the bottom of the pot.
Add lentils and broth: Add lentils and salt and stir until well distributed and coated with spices, then stir in the broth.
Simmer: Cover and bring to a boil, then lower heat to medium low and simmer for 10 minutes.
Add remaining ingredients: Stir in zucchini, mushrooms, and the kabocha cream sauce. Simmer until zucchini is just tender, about 5 minutes.
Season: Turn off heat and stir in lemon/lime juice to taste (start with 1 tbsp). Add more salt if desired. Garnish with cilantro just before serving.
Notes
Spices: Feel free to play around with your favorite spices/whatever you have on hand. Sometimes I like to add curry powder/garam masala in place of some of the turmeric/coriander (respectively). Vegetable Broth: I use Better Than Bouillon.