In a medium bowl, cream together the softened butter and powdered sugar. Stir in the flour and salt until a crumbly dough forms. Press the mixture firmly into the bottom and up the sides of a 9-inch tart pan with a removable bottom. Prick the base with a fork and chill in the freezer for 15 minutes.
Preheat your oven to 350°F (175°C). Line the chilled crust with parchment paper and fill with pie weights or dried beans. Bake for 15 minutes, then remove the weights and parchment. Bake for another 8 to 10 minutes until the crust is lightly golden. Set aside to cool completely.
In a saucepan over medium heat, combine the fresh cranberries, 1 cup of granulated sugar, orange juice, and orange zest. Cook for about 10 to 12 minutes until the cranberries burst and the mixture thickens into a jam-like consistency. Remove from heat and let it cool slightly.
Blend the cooked cranberry mixture until smooth, then press it through a fine-mesh sieve into a clean bowl to remove the skins. Whisk in the eggs and egg yolks. Return the mixture to a clean saucepan over low heat. Whisk constantly while adding the cubed butter, one piece at a time, until the curd is thick enough to coat the back of a spoon.
Pour the warm cranberry curd into the pre-baked tart shell. Smooth the top with a spatula. Place the tart back in the oven at 350°F for about 10 minutes just to set the filling. Remove from the oven and let it cool to room temperature, then refrigerate for at least 2 hours.
While the tart chills, make a simple syrup by boiling ½ cup water and ½ cup sugar. Let it cool until warm but not hot. Toss a handful of fresh cranberries in the syrup, then roll them in the remaining ½ cup of granulated sugar until coated. Place them on a wire rack to dry for 30 minutes.
Just before serving, arrange the sparkling sugared cranberries on top of the chilled tart. You can pile them in the center or create a ring around the edge for a beautiful presentation.