In a mixing bowl, combine the all-purpose flour, powdered sugar, and salt. Add the very cold butter pieces, and using a pastry cutter or your fingers, blend until the mixture resembles coarse crumbs.
Incorporate the egg yolk into the flour mixture and mix until the dough comes together. If the dough feels too crumbly, add a teaspoon of cold water at a time until it holds together.
Shape the dough into a disk, wrap it in plastic wrap, and refrigerate for at least 30 minutes.
Once chilled, preheat your oven to 350°F (175°C). On a lightly floured surface, roll out the dough into a circle about 1/4 inch thick. Transfer it to the tart pan, pressing it into the bottom and up the sides. Trim any excess dough.
Prick the bottom of the crust with a fork to prevent bubbling. Bake in the preheated oven for 15-20 minutes or until lightly golden. Allow it to cool completely.
In a mixing bowl, beat the softened cream cheese until smooth. Gradually fold in the whipped cream until fully combined and fluffy. Spread the mixture evenly over the cooled tart crust.
Arrange the sliced strawberries in rows to create the stripes of the American flag. Place the blueberries in the corner to represent the stars.
To give your tart a beautiful shine, warm the apricot preserves in a small saucepan over low heat until melted. Brush it gently over the fruit for a glossy finish.
Refrigerate the tart for at least 1 hour before slicing. This allows the flavors to meld and the filling to set. When ready to serve, slice and enjoy!