Place the pumpkin in a bowl and sprinkle liberally with salt. Toss to get it all coated, cover and leave overnight. Drain of any juices, wash in cold water, then drain again to remove excess moisture.
Peel and segment the fruit and remove the pith. Tip into a heavy-based pot with all of the remaining ingredients. Bring to the boil over medium heat, then reduce the heat and leave to simmer uncovered, stirring occasionally, for about 40 mins. Cool, then transfer to a sterilised jar and seal.