For the Tart Crust:
In a small bowl, whisk together the egg yolk, heavy cream, and vanilla extract.
In a food processor, pulse the flour, confectioners’ sugar, and salt until combined. Add the chilled butter cubes and pulse until the mixture resembles coarse cornmeal.
With the processor running, add the egg yolk mixture and process until the dough just comes together.
Form the dough into a 6-inch disk, wrap tightly in plastic wrap, and refrigerate for at least 1 hour or up to 4 days.
Let the chilled dough sit at room temperature for 10 minutes, then roll it out into an 11-inch circle on a lightly floured surface. Transfer the dough to a 9-inch tart pan, pressing it gently into the corners and sides. Remove excess dough by running a rolling pin over the top of the pan.
Freeze the dough-lined tart pan for about 30 minutes.
Preheat the oven to 375°F. Line the crust with aluminum foil and pie weights. Bake for 30 minutes, rotating the pan halfway through, until the crust is golden brown. Remove the foil and weights and let the crust cool completely.
For the Lemon Curd:
Preheat the oven to 350°F. Set aside 1 tablespoon of lemon juice for the blueberry layer.
In a medium saucepan, whisk together the remaining lemon juice, lemon zest, egg, egg yolks, honey, and a pinch of salt. Cook over medium-low heat, stirring constantly, until the mixture thickens slightly and reaches 165°F, about 5 minutes.
Remove from heat and whisk in the chilled butter until melted. Strain the curd through a fine-mesh sieve, then stir in the heavy cream.
Pour the warm lemon curd into the cooled tart crust. Bake for 10–12 minutes, until the filling is shiny and slightly jiggly in the center. Let the tart cool.
For the Blueberry Layer:
Purée the blueberries in a food processor until smooth. Strain the purée through a fine-mesh sieve into a medium saucepan, discarding the solids.
Whisk in the honey and a pinch of salt. In a small bowl, whisk together the cornstarch and water, then stir it into the blueberry mixture.
Cook over medium-low heat, stirring constantly, until the mixture thickens and reaches 170°F, about 4 minutes. Remove from heat and stir in the reserved lemon juice.
Pour the blueberry mixture evenly over the lemon curd layer. Tap the tart lightly on the counter to remove any air bubbles. Refrigerate for about 2 hours, until the blueberry layer is set.
To Serve:
Carefully remove the outer ring of the tart pan and slide the tart onto a serving plate or cutting board. Slice and enjoy!