Pickled onion

Pickled onions were a prepared food found on Earth. (TV: World War Three, AUDIO: Invasion of the Daleks)

Mickey Smith had pickled onions (along with pickled eggs and gherkins) in his cupboard. Jackie Tyler used them to kill a Slitheen that had invaded her flat. The vinegar (and therefore the acetic acid) they were pickled in could dissolve a Raxacoricofallapatorian's calcium-based physiology. (TV: World War Three)

Susan Mendes's grandmother sent her pickled onions from Earth. She also left a jar of them for Alby Brook. (AUDIO: Invasion of the Daleks)

In one episode of Steptoe and Son, the old man dumped pickled onions into his bathwater. (PROSE: The Devil Goblins from Neptune)