For the crust: Whisk 1 egg yolk, 1 tablespoon cream, and ½ teaspoon vanilla together in a bowl. Process flour, confectioners' sugar, and salt in a food processor until combined. Scatter chilled butter over the top 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 1 hour.

Let the chilled dough sit on the counter to soften slightly, about 10 minutes. Roll the dough into an 11-inch circle on a lightly floured surface. Loosely roll the dough around a rolling pin and gently unroll it onto a 9-inch tart pan with a removable bottom, letting the excess dough hang over the edge. Ease the dough into the pan by gently lifting the edge of the dough with your hand while pressing into the corners and fluted sides of the pan with your other hand. Run the rolling pin over the top of the pan to remove any excess dough.

Wrap the dough-lined pan loosely in plastic, place on a large plate, and freeze until the dough is chilled and firm, about 30 minutes. Adjust oven rack to the middle position and heat oven to 375ºF (190°C). Set the dough-lined tart pan on a baking sheet, line with a double layer of aluminum foil, covering the edges to prevent burning, and fill with pie weights. Bake until the crust is golden brown and set, about 30 minutes, rotating the pan halfway through baking. Remove weights and foil and let the crust cool.

For the lemon curd: Adjust oven rack to the middle position and reduce oven heat to 350ºF (175°C). Measure out 1 tablespoon of lemon juice and set aside for the blueberry layer. Whisk the remaining lemon juice, lemon zest, egg, egg yolks, honey, and salt in a medium saucepan until smooth. Cook over medium-low heat, stirring constantly with a rubber spatula, until the mixture thickens slightly and registers 165°F (74°C), about 5 minutes.

Off heat, whisk in the chilled butter until melted. Strain the lemon curd through a fine-mesh sieve into a bowl, then gently stir in the heavy cream. Pour the warm lemon curd into the cooled tart crust. Set the tart on a baking sheet and bake until the filling is shiny and opaque and the center jiggles slightly when shaken, 10–12 minutes, rotating the pan halfway through baking. Transfer the tart with the baking sheet to a wire rack and let cool slightly.

For the blueberry layer: Process the blueberries in a food processor until smooth. Strain the purée through a clean fine-mesh sieve into a medium saucepan, pressing on the solids to extract as much liquid as possible. Whisk in the honey and salt. Whisk together the cornstarch and water in a small bowl, then whisk into the strained blueberry mixture. Bring to a simmer over medium-low heat, stirring constantly, and cook until thickened slightly and registers 170°F (77°C), about 4 minutes.

Off heat, whisk in the reserved tablespoon of lemon juice. Pour the blueberry mixture evenly over the cooled lemon filling. Tap the pan lightly on the counter to release any air bubbles, then refrigerate until the blueberry mixture is set and shiny, about 2 hours.

To serve, remove the outer ring of the tart pan, slide a thin metal spatula between the tart and the tart pan bottom, and carefully slide the tart onto a serving platter or cutting board.