01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together flour, sugar, baking powder, baking soda, salt, and lemon zest until well combined.
03 - Add cold butter cubes and cut in using a pastry blender or fingertips until mixture resembles coarse crumbs with some pea-sized pieces remaining.
04 - In a separate bowl, whisk together heavy cream, egg, and vanilla extract until blended.
05 - Pour wet ingredients into dry ingredients. Stir just until dough begins to come together. Do not overmix.
06 - Gently fold in blueberries until evenly distributed. Handle dough minimally to prevent streaking.
07 - Turn dough onto lightly floured surface. Pat into 1-inch thick round. Cut into 8 wedges and transfer to prepared baking sheet.
08 - Brush tops with cream. Bake for 16-18 minutes until golden brown. Cool on wire rack.
09 - Set a heatproof bowl over simmering water. Whisk together eggs, sugar, lemon juice, lemon zest, and salt until smooth.
10 - Cook over simmering water, stirring constantly, until mixture thickens and coats the back of a spoon, about 8-10 minutes.
11 - Remove from heat. Whisk in butter pieces until smooth and melted. Strain if desired. Refrigerate until chilled.
12 - Serve scones warm or at room temperature with a generous spoonful of chilled lemon curd.