1 part vinegar
1 part water
Big pinch of salt
Slice the onions
Very thinly slice the red onions from root to stem and add them to a jar.
Boil the water/vinegar + add onions
Add equal parts vinegar and water to a pot (enough to cover the onions) with a big pinch of salt. Bring to a boil and pour over the onions.
Cover and let sit in the fridge for at least 2 hours before serving. The pink color will get deeper the longer they sit.
Put them on everything.