Preheat the oven to 425F (210C).

Line two baking sheets with parchment paper and set aside.

In a large bowl, whisk together the flour, sugar, baking powder, baking soda, salt and grated lemon peel.

Grate the frozen butter and toss it into the flour mixture. Use a pastry cutter or two knives to work in the butter just until the mixture resembles coarse crumbs. Make a well in the center and pour in one cup of buttermilk. With a rubber spatula, gently toss together the mixture just until it appears moistened.

Turn out the dough on a floured surface. Dust a rolling pin with flour and roll out your dough into a 16 inch square. Scatter the blueberries over the dough.