Beat butter and confectioners' sugar with a mixer on medium speed until pale, 2 to 3 minutes. With machine running, add egg, and beat until fully incorporated. Add orange zest, and beat for 30 seconds. Reduce speed to low, and add flour-salt mixture, beating until just combined. Wrap in plastic, and chill for at least 1 hour.

Make the pastry cream: Combine milk, vanilla bean pod and seeds, and 2 tablespoons granulated sugar in a saucepan. Bring to a simmer over medium heat.

Whisk together egg yolks, cornstarch, and remaining 2 tablespoons granulated sugar in a separate bowl. Slowly add 1/3 cup milk mixture to the egg mixture, whisking to combine. Add egg-milk mixture back to the pot, and cook over medium-high heat, stirring constantly, until mixture thickens, about 2 minutes. Transfer to a mixing bowl, and beat in butter with paddle attachment until combined and cream has cooled, about 5 minutes. Strain into a bowl. Place plastic wrap directly on the surface of the cream, and refrigerate for 2 hours.

Make the tart: Generously butter a 9-inch removable-bottom tart pan. Set aside. Roll out dough on a lightly floured surface to a 10-inch round with 1/4-inch thickness. Fit dough into tart pan, pressing gently along the sides and bottom of pan. Trim excess. Refrigerate or freeze for 30 minutes.

Preheat oven to 350 degrees. Bake until crust is firm and golden brown, about 30 minutes. Let cool on a wire rack.

Prepare citrus fruit: Place citrus segments into a colander to drain. Cover, and refrigerate.

Beat chilled pastry cream with paddle attachment until smooth, about 30 seconds. Set aside. Whip heavy cream using the whisk attachment until stiff peaks form. Carefully fold whipped cream into pastry cream.