01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together the flour, sugar, poppy seeds, lemon zest, baking powder, baking soda, and salt until well combined.
03 - Add the cold, cubed butter to the flour mixture. Use a pastry blender or your fingertips to cut the butter into the flour until the mixture resembles coarse crumbs.
04 - In a separate bowl, whisk together the heavy cream, egg, lemon juice, and vanilla extract until smooth.
05 - Pour the wet ingredients into the dry ingredients. Stir gently until just combined. Be careful not to overmix.
06 - Turn the dough onto a lightly floured surface. Gently knead a few times to bring it together, then pat into a 1-inch thick circle about 7 inches wide. Cut into 8 wedges.
07 - Transfer the wedges to the prepared baking sheet, spacing them slightly apart. Brush the tops with a little extra cream.
08 - Bake for 16-18 minutes, or until golden brown. Transfer to a wire rack to cool completely.
09 - While scones cool, whisk powdered sugar with lemon juice until smooth and drizzle-consistency.
10 - Drizzle the glaze over cooled scones before serving.