Borscht

The soup began its existence from trimmings of cellared vegetables consumed throughout the winter months. Most families had a container, usually a kettle or stove pot, kept outside to store those trimmings. Around the first spring thaw that pot was placed on the fire and cooked into a soup-like meal. One of the primary vegetables of the Slavic diet consumed during the winter months was beets. Hence the recipe morphed into what is traditionally known as a beet soup.
-Wikipedia