Blitz the tomato, chilli and garlic in a blender until smooth.
Scrape the mixture into a saucepan and stir in the remaining ingredients. Bring to the boil over high heat, then reduce the heat and simmer for 30–35 minutes, or until the mixture thickens, stirring regularly.
Leave to cool slightly, then spoon into a sterilised jar, seal and refrigerate. The relish can be used strai