- 8 red onion, sliced
- 100g caster sugar
- 100ml red wine vinegar
- 100ml red wine
- dash grenadine syrup
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Place the onions and sugar in a saucepan, cover and cook over medium heat until soft, about 10 mins. Pour in the red wine vinegar and red wine, then simmer uncovered until the liquid has reduced and the mixture is sticky, about 10 mins more. Add the grenadine syrup and mix well. Leave to cool, then transfer to a sterilised jar and seal.
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If you want to use a slow cooker...
Mix the onions and sugar in the slow cooker pot then cover and cook on High for 2-3 hours, stirring occasionally until soft and caramelised. Add the red wine vinegar and red wine and cook, uncovered, on High for another 2-3 hours until sticky. Stir in the grenadine, leave to cool then transfer to sterilised jars.