Preheat the oven to 375 degrees F.
Roll the dough into a 12-inch diameter circle that is about 1/4-inch thick. Transfer the dough to a 10-inch tart pan by rolling the dough around the rolling pin. Line the tart pan with the dough. Dock the dough and set aside.
Make the almond cream. Spread a layer of almond cream inside the tart. Pit and quarter the fresh apricots. Arrange them on top of the almond cream by standing them on end. Sprinkle slivered almonds on top of the tart and bake for about 40 minutes. Dust with confectioners' sugar.
Place the almond flour, cake flour and cold butter in the mixing bowl and mix until combined. Add the salt and powdered sugar. Mix until combined. Add the egg and mix until combined. Shape into a disk, wrap in plastic and refrigerate for about 1 hour to chill dough.
Roll the dough to the desired size on a lightly floured work surface.
Baking instructions vary and will be specified in any recipe using this dough. The dough will keep, well wrapped in plastic wrap in the refrigerator for 1 week or in the freezer for 1 month. Thaw the dough in the refrigerator until ready to use. If you want to store the dough already rolled into a tart pan, wrap it in plastic wrap.
It is possible to buy almond flour (use 1 cup if you do) but it just as easy to make your own. Place the slivered almonds (no skin preferred) and granulated sugar into the food processor. Pulse until the almonds and sugar reach the consistency of flour. It is best to pulse because the heat of the blade will cause the release of the oil from the almonds.
Mix in the flour. Mix in the butter. Add the egg and mix until the mixture becomes light and creamy. Do not overmix or the gluten in the flour will overdevelop and the almond cream will lose its delicate texture when baked.