In a food processor, pulse together the pureed beets and buttermilk until completely smooth and combined.
Transfer the mixture to a bowl, cover, and refrigerate until ready to use or for up to a day.
Preheat oven to 425˚F (220˚C). Line a large baking sheet with parchment or lightly grease.
In a large bowl, combine the flour, sugar, baking powder, and salt.
Quickly cut in the chilled and diced butter using a dough blender, two forks, or your fingers until blended and no pieces are larger than a pea.
Make a well in the center of the buttery mixture and add the cooled beet puree and buttermilk mixture.
Mix just until the dough comes together. If the mixture still won't come together, add a little more buttermilk a splash at a time. If the mixture is too wet, add a little more flour.
On a lightly floured surface, pat the dough into a rectangle about 3/4 inch (2 centimeters) thick, flouring the top only as needed to keep it from sticking to your hands.
With a sharp knife, cut the dough into 9 equal squares or use a 2 1/2 inch (6 centimeter) wide round cutter to cut out 8-10 round biscuits, being careful not to twist the cutter as you press down.
Place the biscuits 1-2 inches (2.5-5 centimeters) apart on the prepared baking sheet. If desired, brush the tops with additional buttermilk.
Bake in preheated oven until flaky and bottoms are lightly golden brown, 13-15 minutes.
These Beet Biscuits are best warm from the oven.