01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together flour, sugar, poppy seeds, lemon zest, baking powder, baking soda, and salt.
03 - Add cold, cubed butter to dry ingredients. Using a pastry cutter or fingertips, incorporate butter until mixture appears as coarse crumbs.
04 - In a separate bowl, whisk heavy cream, egg, lemon juice, and vanilla extract until smooth.
05 - Pour wet ingredients into dry mixture and gently stir just until combined, avoiding overmixing.
06 - Turn dough onto a lightly floured surface and pat into a 1-inch thick round.
07 - Cut dough into 8 wedges and place on the prepared baking sheet with slight spacing between pieces.
08 - Lightly brush the tops of the scones with additional heavy cream.
09 - Bake for 18 to 20 minutes until golden brown and cooked through. Transfer to a wire rack to cool.
10 - Whisk powdered sugar with enough lemon juice to create a thick but pourable glaze.
11 - Drizzle glaze over cooled scones and allow to set before serving.