To make the soup heat a large saucepan over a medium heat and add the oil and onions along with a pinch of salt. Fry the onions until golden. Add the magic sauce and cook for 1 minute or until fragrant. Add the pumpkin and toss in the onions and sauce and allow to brown slightly.
To make the magic sauce, toast the cumin and coriander seeds in a frying pan over a medium heat until fragrant. Set aside to cool. Once cooled add to a food processor fitted with a steel blade and process until a powder forms. Add the remaining ingredients and process until you have a smooth paste. Decant into a sterilised jar and refrigerate.