In a large pot, bring water to a boil. Add the grated beets and cook until tender, about 10-15 minutes. Drain and let the beets cool completely.
In a large mixing bowl, combine the cooked beets, diced cucumbers, chopped hard-boiled eggs, sliced radishes, chopped green onions, and fresh dill.
In a separate bowl, whisk together the kefir or buttermilk, cold water, lemon juice or vinegar, salt, and pepper.
Pour the kefir mixture over the vegetable mixture and stir until well combined.
Cover the bowl and refrigerate the kholodnik for at least 2 hours, or until thoroughly chilled. This allows the flavors to meld together.
Ladle the chilled kholodnik into bowls.
Garnish with a dollop of sour cream on top and additional fresh dill if desired.
Enjoy your meal!