Preheat oven to 425°. Spray a cast-iron wedge pan with baking spray with flour.
For scones: In a large bowl, stir together flour, sugar, baking powder, salt, zest, and baking soda. Using a pastry blender or 2 forks, cut butter into flour mixture until crumbly. In a small bowl, whisk together buttermilk and egg until smooth. Add buttermilk mixture to flour mixture, stirring just until combined. (Dough will be wet.).
Turn out dough onto a heavily floured surface. Fold dough in half until it becomes comes together, 5 to 6 times. Pat or roll dough into a 1½-inch-thick circle. Cut dough into 8 wedges. Place wedges in wells of prepared pan.
Bake until golden brown, about 13 - 15 minutes.
For drizzle: In a small bowl, whisk confectioners’ sugar, buttermilk, and lemon zest and juice. Drizzle over warm scones. Serve immediately.