Heat the oil in a saucepan. Add the carrots, cinnamon and ginger and stir for a few minutes. Pour in the water and bring to the boil. Reduce the heat and simmer for about 15 minutes until the carrots are cooked.
In the meantime, toast the cumin seeds in a saucepan until dark and grind to a powder in a mortar; set aside.
Liquidise the carrot mixture in a blender until smooth. Add the orange juice, sugar, powdered cumin and salt to taste. Heat up again and serve at once.