1. Pour the capsicums, chillies, ginger and garlic into a food processor and pulse until very finely chopped. Scrape into a heavy-bottomed pan with the tomatoes, sugar and vinegar, then bring everything to the boil. Skim off any scum that comes to the surface, then turn the heat down and simmer for about 50 mins, stirring occasionally.
2. Keep stirring when the jam starts to get sticky, and continue cooking for 10-15 mins more. Cool slightly, transfer to sterilised jars and seal the lids, then leave to cool completely. Keeps for 3 months in a cool, dark cupboard – refrigerate once opened.