In a food processor, pulse together the flour, sugar, and salt. Add the cold, cubed butter and pulse until the mixture resembles coarse crumbs. With the motor running, gradually add the ice water, one tablespoon at a time, until the dough just comes together. Be careful not to overmix.

Alternatively, in a large bowl, whisk together flour, sugar, and salt. Cut in the cold butter using a pastry blender or your fingertips until crumbly. Add ice water a tablespoon at a time, mixing until the dough forms a ball.

Press the dough evenly into the bottom and up the sides of a 9-inch tart pan with a removable bottom. Prick the bottom of the crust several times with a fork. Cover with plastic wrap and chill in the refrigerator for at least 30 minutes.

Preheat oven to 375°F (190°C). Line the chilled crust with parchment paper and fill with pie weights or dried beans. Bake for 15-20 minutes, or until the edges are lightly golden. Remove the parchment paper and weights and bake for another 5-7 minutes, or until the bottom is lightly golden. Remove from oven and let cool slightly while you prepare the filling.

In a medium bowl, whisk together the egg yolks, whole eggs, granulated sugar, lemon juice, and lemon zest until well combined.

Pour the mixture into a medium saucepan. Cook over medium-low heat, whisking constantly, until the mixture thickens enough to coat the back of a spoon (about 5-8 minutes). Do not boil.

Remove from heat and immediately stir in the melted butter until fully incorporated. Strain the lemon curd through a fine-mesh sieve into a clean bowl to remove any cooked egg bits and zest, ensuring a smooth filling.

Pour the warm lemon curd into the par-baked and slightly cooled shortbread crust.

Reduce oven temperature to 325°F (160°C). Carefully transfer the tart pan to the oven and bake for 25-30 minutes, or until the center is just set but still slightly wobbly. The edges should be firm.

Remove the tart from the oven and let it cool completely on a wire rack. This will take at least 2-3 hours at room temperature, then transfer to the refrigerator to chill for another 2 hours or until thoroughly chilled and firm.

While the tart is chilling, prepare the blueberry topping. In a small saucepan, combine the blueberries, sugar, cornstarch, and lemon juice. Cook over medium heat, stirring frequently, until the mixture thickens and the blueberries begin to burst, about 5-7 minutes.

Remove from heat and let cool completely. The topping will thicken further as it cools.

Once the tart is fully chilled and firm, carefully remove it from the tart pan. Spread the cooled blueberry topping evenly over the lemon curd. Garnish with fresh blueberries if desired.

Slice and serve chilled. Enjoy!