In a medium bowl, whisk together one egg yolk, heavy cream, and vanilla extract until smooth. In a food processor, pulse together all-purpose flour, confectioners’ sugar, and kosher salt until combined. Add in the chilled, cubed unsalted butter and process until the mixture resembles coarse crumbs. Gradually add the egg mixture and pulse until a dough forms. Shape the dough into a disk, wrap it in plastic, and refrigerate for at least 1 hour.

Preheat your oven to 350°F (175°C). Roll out the chilled dough on a floured surface until it's about 1/8 inch thick. Carefully fit the dough into a 9-inch tart pan, pressing it into the corners. Refrigerate for 15 minutes to firm up. Line the crust with parchment paper, fill with pie weights or beans, and bake for 20-25 minutes, until golden. Remove the weights and let the crust cool completely in the pan.

In a medium saucepan, combine freshly squeezed lemon juice, lemon zest, eggs, and honey. Cook over medium heat, whisking constantly until the mixture reaches 165°F and thickens slightly. Remove from heat and stir in cold unsalted butter until melted. Strain the lemon curd through a fine sieve to remove any lumps, then pour into the cooled tart shell, smoothing it evenly. Return the tart to the oven for an additional 10-12 minutes, until set but slightly jiggly.

In a blender, puree the blueberries until smooth. Strain the mixture through a fine mesh sieve to remove seeds, pressing to extract as much liquid as possible. In a small saucepan, combine blueberry puree with honey and cornstarch over medium heat. Simmer for about 4 minutes, stirring frequently, until thickened. Carefully pour the blueberry layer over the lemon curd in the tart shell, spreading it evenly.

Cover the tart loosely with plastic wrap or foil and refrigerate for at least 2 hours, allowing the layers to set and flavors to meld. Once set, remove from the fridge, and if desired, garnish with fresh berries or a dollop of whipped coconut cream.