Prepare the Crust: In a food processor, combine flour, confectioners' sugar, and kosher salt. Add butter and pulse until crumbly. Mix in egg yolk, heavy cream, and vanilla until dough forms. Wrap in plastic and refrigerate for 1 hour.

Roll and Bake Crust: Preheat oven to 350°F (175°C). Roll dough on a floured surface into an 11-inch circle. Fit into 9-inch tart pan and trim excess. Bake until lightly golden, about 20 minutes.

Make Lemon Curd: In a saucepan, whisk egg, yolks, lemon juice, lemon zest, honey, and kosher salt. Heat over medium-low, stirring until thickened. Remove from heat, stir in butter and heavy cream, strain into cooled crust.

Bake Lemon Layer: Return tart to oven and bake for 10-12 minutes until filling is set but jiggles slightly in the center. Cool at room temperature.

Prepare Blueberry Filling: In a blender, puree blueberries until smooth, strain to extract liquid. In saucepan, combine blueberry juice, honey, and cornstarch. Simmer over medium heat until thickened.

Assemble Tart: Once lemon curd cools, pour blueberry filling over the top. Refrigerate until set, about 2 hours.