To make the sauce, heat the oil over a medium heat, add the onion and garlic, and cook for 2-3 minutes. Add the curry paste, tomato paste, and cayenne pepper, stir, and cook for another 2-3 minutes. Add the remaining ingredients, except the cream, and bring to a boil, then simmer for 10 minutes.
Leave to cool, then purée the sauce in a blender. Taste and adjust seasoning if necessary. I