Place the onions in a large preserving pan with a little of the vinegar and cook for a few minutes to soften. Add the apples and the raisins or dates and continue cooking until pulpy.
Add the beetroot, ginger, salt and half the remaining vinegar. Simmer gently until thick. Stir in the sugar and remaining vinegar and continue cooking until thick again.
Pot into cooled, sterilised jars and seal with vinegar proof lids. Store for 6-8 weeks before using.