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 evenly distributed.
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. Pour into dry ingredients and stir just until combined—do not overmix.
05 - Gently fold in blueberries, taking care not to crush them or overwork the dough.
06 - Turn dough onto a lightly floured surface. Pat into a 1-inch thick round. Cut into 8 wedges and transfer to prepared baking sheet, spacing 2 inches apart.
07 - Brush tops lightly with cream. Bake 16–18 minutes until golden brown and firm to touch. Transfer to a wire rack to cool.
08 - While scones bake, set a heatproof bowl over a saucepan of simmering water. Whisk together eggs, sugar, lemon juice, lemon zest, and salt.
09 - Cook, stirring constantly, until thickened enough to coat the back of a spoon, about 8–10 minutes. Remove from heat and whisk in butter until smooth. Strain through a fine sieve if desired. Chill before serving.
10 - Serve scones warm or at room temperature with a generous spoonful of lemon curd.