Toss the diced butternut squash in about 1tbsp of oil with some salt and pepper, and spread it out in a single layer on a baking tray. Roast at 190°C (Gas Mark 5 / 375°F) for around 30 minutes, until soft and slightly crispy.
Heat the remaining 1tbsp of oil in a large pan or wok, and add the diced onion, celery, garlic, ginger and sweet potato. Cook over a medium-low heat for around 10 minutes, stirring regularly, until the vegetables are soft.
Turn the heat down to low, add the spices (ground cumin to turmeric) to the pan, and cook for a couple more minutes, stirring constantly, to toast the spices. Then add the tomato puree, coconut milk, halved cherry tomatoes, and water. Bring to a simmer, and cook for 10-15 minutes, until the tomatoes have begun to break down, and all the other vegetables are soft.
Carefully transfer the sauce to a blender, and blitz until smooth. Return to the pan, and add the cooked black beans and roasted butternut squash.
When you're ready to serve, stir through the fresh spinach and chopped coriander - the heat of the sauce will wilt the spinach. Serve with rice or naan bread.