Preheat the oven to 375°F. Spray a baking sheet with nonstick spray or line with parchment paper.
In a large bowl, whisk together the flour, sugar, baking powder, baking soda and salt. Cut in the butter with a pastry blender or 2 knives until the mixture resembles fine crumbs. Add the buttermilk, eggs, poppy seeds and lemon zest; stir with a fork until the dry ingredients are moistened.
Transfer the dough to a lightly floured surface and pat into a 7-inch circle. Slide the dough onto the prepared baking sheet; cut into 8 pie-shaped wedges, cutting to, but not through, the bottom of the dough. (Do not separate the wedges).
Bake for 20 to 23 minutes or until golden brown. Transfer to a wire rack; sift powdered sugar over top. Gently cut through the wedges with a serrated knife to separate and serve.
Notes
Alternative: top the scones with a lemon glaze instead:
In a medium bowl, whisk together 1 cup of powdered sugar with 3 tablespoons of freshly squeezed lemon juice. Drizzle the lemon glaze over the baked scones and give that glaze time to set before serving.