Preheat the oven to 425°F. Line a rimmed baking sheet with parchment paper.
Whisk together the flour, baking powder, baking soda, sugar, salt, and lemon zest. Grate the stick of butter using a box grater, then scatter the shreds over the dry ingredients.
Toss the butter with the dry ingredients and, using your hands, squeeze it gently to disperse it throughout the flour.
Add the buttermilk and the blueberries, and mix gently with a spatula until you don't see any dry patches in the dough. The dough will still be shaggy but when pinched, it should hold together. If the mixture seems dry, add a tablespoon more buttermilk as needed.
Turn the crumbly dough out into the center of a large tea towel, grab the sides and twist the mass into a beggar's purse, squeezing gently to help it form a disk. Open the tea towel and gently pat the dough as needed to help it come together.
