Preheat oven to 450°F. Spray an 8x8-inch baking dish with nonstick cooking spray. Set aside.
Grate butter onto a sheet of parchment paper using the fine edge of a grater. Transfer the grated butter to the freezer while preparing other ingredients.
In a large bowl, whisk together flour, sugar, baking powder, lemon zest, and baking soda.
Using a fork, incorporate the frozen grated butter into the dry ingredients until the mixture resembles coarse crumbs. Add 1 cup of buttermilk and stir until just combined. Be careful not to overwork the dough.
Transfer the dough onto a floured surface and gently press it into a flat square. Fold over once, and press down. Fold over again, and press down. Fold over for a third time and press the dough into squares measuring about 1 ½ inches thick. (You could also make the thickness 1-inch if you want 8 biscuits.)
Using a biscuit cutter or round kitchen glass, cut out biscuits. (I used a 3-inch cutter and got 5 large biscuits with enough dough left over for one more small biscuit.) Place the biscuits in the prepared dish, ensuring they are slightly touching. Brush the tops of the biscuits with the remaining 1 tablespoon of buttermilk.
Bake for 14-16 minutes, or until the biscuits are golden brown on top and cooked through. Allow the biscuits to cool to room temperature before assembling.