1. Boil the beetroots until just tender, then peel and slice them.
2. In a pot, mix vinegar, water, sugar, salt, and mustard seeds.
3. Heat until the sugar and salt are dissolved.
4. Pack beetroot slices into a clean jar.
5. Pour the hot brine over the beets, covering completely.
6. Let it cool to room temperature, then refrigerate.
7. Ready to eat after 2 days, but tastes better after a week
