A beet is a beetroot, the taproot portion of the beet plant.
Beets are commonly eaten vegetables in Westeros and beyond. They are very popular in Volantis. Some characters do not like beets, most notably Prince Tommen. Sweet beets are grown in profusion in Volantis, and are served with almost every meal. There, they make a cold soup of the beets which is as thick and rich as purple honey.
A Clash of Kings
A Feast for Crows
When Kevan Lannister meets with Queen Regent Cersei Lannister for dinner, they eat a simple supper of beets and bread and bloody beef When Cersei Lannister has Falyse Stokeworth and her husband, Ser Balman Byrch, as guests for dinner buttered beets feature on the menu.
A Dance with Dragons
When I'm king in my own right, I'm going to outlaw beets.—Tommen to Cersei Lannister