01 - Set oven to 400°F and line a baking sheet with parchment paper.
02 - Whisk together flour, sugar, poppy seeds, lemon zest, baking powder, baking soda, and sea salt in a large bowl.
03 - Cut cold cubed butter into dry ingredients using a pastry cutter or fingertips until mixture resembles coarse crumbs.
04 - Whisk cream, egg, lemon juice, and vanilla extract in a separate bowl until well combined.
05 - Pour wet ingredients into dry mixture and stir gently just until combined; avoid overmixing.
06 - Turn dough onto a lightly floured surface and pat into a 1-inch thick round.
07 - Slice dough into 8 wedges and place on the prepared baking sheet, spacing them slightly apart.
08 - Lightly brush the tops of each wedge with additional heavy cream.
09 - Bake for 18 to 20 minutes or until golden brown and cooked through, then transfer to a wire rack to cool.
10 - Whisk powdered sugar with enough lemon juice to create a thick yet pourable glaze.
11 - Drizzle glaze over cooled scones and allow to set before serving.