1. 1. Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.2. In a large bowl, whisk together the flour, sugar, baking powder, and salt.3. Add the cold, cubed butter to the flour mixture and use a pastry cutter or your fingers to blend until the mixture resembles coarse crumbs.4. In a separate bowl, combine the buttermilk, egg, lemon juice, lemon zest, and vanilla extract.5. Pour the wet ingredients into the dry ingredients and stir until just combined. Fold in the poppy seeds.6. Turn the dough out onto a lightly floured surface and gently knead a few times until it comes together. Pat the dough into a circle about 1 inch thick.7. Cut the dough into wedges (like a pizza) and place them on the prepared baking sheet.8. Bake for 15-20 minutes, or until golden brown.9. While the scones are baking, prepare the glaze by mixing the powdered sugar, lemon juice, and lemon zest in a small bowl.10. Once the scones are out of the oven, drizzle the glaze over the warm scones and let cool slightly before serving.