White Onion
brown onion · yellow onion · Spanish onion (larger variety) · Allium cepa
The white or brown onion is the foundational aromatic of cooking in almost every culinary tradition worldwide. Raw, it is pungent and sharp from sulphur compounds that form when the cell walls are broken (and cause the eye irritation, via volatile sulphenic acids). Cooked, these compounds evaporate and the onion's natural sugars — roughly 5g per 100g — develop into sweetness. Completely caramelised, an onion is barely recognisable as the same ingredient.
Raw: pungent, sharp, eye-stinging. Softened: sweet, mellow, deeply savoury. Caramelised: molasses-like sweetness with remarkable complexity. The range from raw to fully caramelised is as wide as almost any single ingredient in the kitchen.
Crisp and watery raw with distinct concentric layers. With brief cooking: softened but still retaining some structure. After 45–60 minutes of gentle cooking: completely collapsed, silky and translucent.
Cool, dry, dark, well-ventilated storage. Never refrigerate whole uncut onions — cold disrupts the cell structure. Halved or sliced onions refrigerate well, covered, for 2–3 days.
Halve through the root (not the ends) before peeling to keep the layers intact. Chill for 15 minutes before cutting to slow the release of eye-irritating compounds. For consistent dice: make parallel cuts toward the root end, horizontal cuts through the thickness (for large onions), then slice across.