Put the sweet potatoes, squash, onion and garlic on a baking sheet. Sprinkle over the cumin seeds and drizzle with the oil. Place in a preheated oven, 200°C (400°F), Gas Mark 6, and roast for 25–30 minutes until tender and golden.
Tip the roasted vegetables into a large saucepan with the chilli flakes and stock, bring to the boil and simmer for 10 minutes.
Stir in the remaining ingredients, heat through until piping hot and then purée in a food processor or blender until smooth. Serve, garnished with a pinch of chilli flakes, and with toasted gluten-free bread.