Mix together the flour, cornmeal, sugar and salt together in a large bowl.
Using a pastry cutter, cut the butter into the mixture until it resembles coarse meal (pea-sized bits with a few larger bits of butter is ok too). You can also do this in a stand mixer or food processor.
Using either your fingers or a spatula, stir in the buttermilk, a tablespoon at a time. The dough should be moist and slightly sticky, but not wet, with no big pockets of dry flour remaining.
Fold the dough onto its self until all flour is incorporated, forming the dough into a ball. Use a light hand to keep the butter from melting.
Flatten the ball into a disc and wrap tightly with plastic wrap.
Refrigerate the dough for one hour or for up to three days.
Line a cookie sheet with parchment paper.
Place the dough on a lightly floured surface or a non-stick rolling mat. Roll from the center outward, rotating the dough 180 degrees, with your hands, every so often. This helps keep its round shape and prevents sticking. Add a little more flour if needed to prevent sticking.
Roll the dough to about 1/8" thick and about 12" round. Transfer the dough onto the parchment lined cookie sheet.
Chill for 20 minutes.