Davidson's plum (Davidsonia spp.) is a deep-purple, plum-shaped Australian rainforest fruit prized for a ferocious sourness — not a true plum at all, its blood-red flesh is far too acidic and astringent to eat raw, so it is cooked down into vivid jams, sauces, syrups and wine and has become a signature "bush tucker" ingredient of modern Australian cuisine.