Preheat oven to 375 F. Grease a baking sheet; set aside.
In a large bowl, whisk together flour, 1/4 cup sugar, baking powder, and salt.
Cut in butter until the mixture looks like small pebbles.
Pour in 1/2 cup buttermilk, and mix to make a sticky mixture. Continue adding buttermilk as needed to make the dough.
On a heavily floured surface, pat dough into an 8x12-inch rectangle. If dough is too sticky, knead a little more flour in to make a workable dough. I like to use a silicone baking mat for this because it makes it really easy to roll up the biscuits.
Stir together remaining sugars and cinnamon, and sprinkle evenly over dough.
Roll up the dough lengthwise.
Using a serrated knife or unflavored floss, cut into 8 biscuits.
Place biscuits on prepared baking sheet.
Bake for about 14-20 minutes, or until the biscuits are golden brown.
Notes
We like the biscuits as-is, but they're also good topped with a simple icing.