01 - Preheat your oven to 400°F and line a baking sheet with parchment paper to prepare for baking.
02 - In a large bowl, whisk together the flour, sugar, baking powder, baking soda, salt, and lemon zest until thoroughly combined.
03 - Add the cold cubed butter to the flour mixture. Use a pastry cutter or your fingertips to work the butter into the flour until the texture resembles coarse crumbs with some pea-sized pieces remaining.
04 - In a separate bowl, whisk together the heavy cream, egg, and vanilla extract until fully blended.
05 - Pour the wet mixture into the dry ingredients. Stir gently with a spatula just until the dough begins to come together. Do not overmix.
06 - Gently fold in the fresh blueberries using a light touch to avoid crushing or discoloring the dough.
07 - Turn the dough onto a lightly floured surface and gently pat it into a 1-inch-thick circle. Use a knife to cut the circle into 8 equal wedges, then transfer them to the prepared baking sheet with space between each.
08 - Brush the tops of each scone with a light coating of heavy cream. Bake for 18 to 22 minutes until the tops are golden brown. Let cool on a wire rack.
09 - While scones bake, whisk together the lemon juice, lemon zest, sugar, and eggs in a small saucepan. Add the cubed butter.
10 - Place the saucepan over medium-low heat and stir constantly with a whisk or spatula for 8 to 10 minutes until the mixture thickens enough to coat the back of a spoon. Do not allow it to boil. Remove from heat and let cool; the curd will continue to thicken as it cools.
11 - Serve the scones warm or at room temperature with a generous spoonful of chilled lemon curd spread on top or on the side.