In a bowl combine sugar, flour and baking powder. Grate in the frozen butter and mix until it resembles coarse meal. In separate bowl, mix the egg, maple syrup, lemon zest, orange zest and buttermilk.
Add the blueberries to the dry ingredients. Pour the wet ingredients into the dry and mix gently. Pour onto a floured surface and gently bring dough together. Pat down with your hands until ½ inch (1cm) thick.
Cut into squares or circles (your choice). Place on parchment sheet lined baking tray. Bake for 10-12 minutes into a pre-heated 400°F (200°C) oven.