Whisk together the flour, sugar, and salt in a large bowl. Cut in the cold butter until the mixture resembles coarse crumbs. Add the egg yolk and 2 tablespoons of ice water, mixing just until the dough comes together. Add the remaining tablespoon of water only if needed.

Press the dough into a disk, wrap it, and chill for 30 minutes.

Preheat the oven to 375°F. Roll the chilled dough on a lightly floured surface into a circle large enough for a 9-inch tart pan. Fit it into the pan, trim any excess, and prick the base lightly with a fork.

Line the crust with parchment paper and fill with pie weights or dried beans. Blind bake for 15 minutes. Remove the parchment and weights, then bake for 8 to 10 minutes more until lightly golden. Set aside.

Combine the blueberries, sugar, and lemon juice in a small saucepan over medium heat. Cook for 4 to 5 minutes until the berries begin to burst.

Stir together the cornstarch and water, then add the slurry to the blueberry mixture. Cook for 1 to 2 minutes more until slightly thickened. Mash or blend lightly for a smoother texture if desired, then cool briefly.

Whisk together the sugar and eggs until smooth. Add the lemon juice, lemon zest, heavy cream, flour, and salt, and whisk until fully combined.

Pour the lemon filling into the pre-baked crust. Spoon dollops of the blueberry mixture over the top and swirl gently with a skewer or knife.

Bake for 18 to 22 minutes, until the edges are set and the center still has a slight wobble.

Cool completely at room temperature, then chill for at least 2 hours before slicing. Garnish with fresh blueberries and lemon wedges before serving.