In a mixing bowl, whisk together the egg yolk, heavy cream, and a splash of vanilla. In a food processor, combine the all-purpose flour, confectioners’ sugar, and kosher salt. Add chilled butter and pulse until the mixture resembles coarse crumbs. Gradually mix in the egg mixture until it forms a cohesive dough. Shape it into a disk, wrap it in plastic, and chill for 1 hour.

Roll out the dough on a lightly floured surface to fit a 9-inch tart pan. Press the dough into the pan and refrigerate for 15 minutes to prevent shrinking. Preheat your oven to 350°F (175°C) and bake the crust for 20-25 minutes until golden brown. Allow to cool completely.

In a medium saucepan, whisk together lemon juice, lemon zest, eggs, and honey. Cook over medium heat, stirring continuously until the mixture thickens slightly and reaches 165°F (74°C). Remove from heat and whisk in cold butter until melted and smooth. Strain the curd into the cooled tart shell.

Puree the blueberries until smooth. Strain to remove seeds, return to saucepan, add honey and cornstarch, stirring to combine. Simmer gently for 4 minutes until thickened. Pour over the lemon curd layer and spread evenly.

Refrigerate the assembled tart for at least 2 hours to let the layers set. Garnish as desired, slice, and serve chilled.