What does it mean to dream about onion?
An onion usually stands for hidden layers, things that bring tears, and what is revealed only by peeling back.
Four ways to read it
Each reading below comes from a named tradition and a cited source, so you can see where it came from and decide what fits your dream.
Freud
Freud would read the onion's sting as a feeling that surfaces against your will, tears drawn out without true sorrow. The peeling of layers can stand for uncovering what lies beneath a manner or a defence. The bite of it may point to a sharpness you handle carefully.
After Freud, The Interpretation of Dreams (Brill trans., 1913), public domain.Jung
Jung might see the onion as an image of the self in layers, each skin hiding another beneath. Peeling it can mark the work of looking inward, with no single core to reach. Ask what you are uncovering and what it costs you to look.
Jungian concept (our summary).Modern
Continuity ties the onion to waking thoughts of cooking or, more figuratively, to peeling back a complicated matter. It may follow a day of getting to the bottom of something. Notice whether the tears felt like release or strain.
Continuity hypothesis (our summary).Mythological
The onion was held sacred in old Egypt, its many layers taken as an image of eternity and the cosmos. Across cultures the layered bulb stood for hidden depths and the mystery of what lies within.
Rosmerta Publishing editorial synthesis (after Frazer; Brewer).