Heat oil in a large saucepan over medium heat. Add onion; cook and stir until soft, 1 to 3 minutes. Add curry powder and chile; cook and stir 2 to 3 minutes more, adding a splash of water if needed to prevent burning. Stir in coconut milk. Add butternut squash and potatoes. Reduce heat and simmer until vegetables are tender, about 30 minutes.
Season with cumin, coriander, turmeric, cayenne, cinnamon, salt, and pepper.
