Pickled Red Onions

Ingredients

• Red onions
• Vinegar
• Water
• Salt

Method

Slice the red onions from root to tip into thin, even half-moons — aim for 3mm or thinner. This matters because thin slices allow the acid-in-cooking to penetrate quickly and evenly, and they soften without turning to mush. Pack them into a clean jar, pressing down lightly as you go.

Combine equal parts water and vinegar (by volume) in a pot — white wine vinegar works well, but rice vinegar will give you a gentler, slightly sweeter result. Add 10g of salt per 250ml of liquid (roughly 2% by weight). This ratio is precise: too little salt and the onions soften to slime; too much and they stay rigid. Bring to a rolling boil. The heat activates the acetic-acid, which denatures the cell walls in the onion layers and forces out their liquid, concentrating the flavour while the acid replaces it. A boil matters here — you need that agitation to help the brine penetrate the tight layers.

Pour the brine over the onions as soon as it reaches a boil, then leave the jar uncovered to cool. The onions will begin their colour shift almost immediately as the anthocyanin pigments respond to the acidic environment, but patience is required. Four hours in the fridge gives you a pale pink; twelve hours gives you a deep magenta that's properly set. The longer they sit, the softer they become and the more the flavour integrates. They'll keep for two weeks sealed in the fridge, though they're best at peak texture — tender but still with a slight resistance — within the first week.

Use these as a sharp counterpoint to fatty foods: on pulled pork, over chorizo and beans, alongside rich fish like mackerel. The pickled-vegetables will cut through fat and add a bright, acidic snap that lifts a dish. Don't discard the brine once the onions are eaten — it's excellent for dressing grains or sharpening a vinaigrette.