Peel the horseradish root and cut it into small cubes. Place in a food processor and start with just 3 to 4 cubes, (80 grams). Process until well ground. Alternatively, you can also grate horseradish on small holes of a box grater. Make sure to keep windows open because the aroma is powerful. I also suggest using gloves while working with the horseradish.
Add the beets, vinegar, sugar, and salt; process until everything is combined.
Taste and correct flavors. If needed, add more horseradish and process everything together again.
Transfer into a small jar and keep in the refrigerator for up to two weeks.