Here’s how it’s done:
Prepare the pickled onions the day before:
- Peel and halve the red onion and cut into thin slices. Place the onions in an airtight container.
- Mix the white wine vinegar, water, sugar and salt in a small saucepan and heat briefly until the sugar has completely dissolved. The liquid does not necessarily have to boil, but this will not harm it.
- Pour the water and vinegar mixture over the onions, cover with an airtight lid and leave for 24 hours.