In a KitchenAid or stand mixer fitted with the paddle attachment, or in a bowl with a rubber spatula, cream the butter and sea salt on medium speed for about 60 seconds. DO NOT WHIP— this would incorporate too much air into the butter. Air bubbles make the final dough puff when you bake it. They also make the dough porous, which would allow moisture from the filling to get through the dough and make your tart soggy. There’s nothing worse than a tart or pie with a soggy crust.
Scrape down the sides of the bowl and the paddle with a rubber spatula and add the confectioners’ sugar. Combine with the butter at low speed. Scrape down the sides of the bowl and the paddle.
Add the almond flour and vanilla and combine at low speed.
Gradually add the eggs and one-quarter (55 grams or ½ cup) of the cake flour. Beat at low speed until just incorporated. Stop the machine and scrape down the bowl and the paddle.
Gradually add the remaining flour and mix just until the dough comes together. It will feel soft to the touch but it won’t be sticky. DO NOT OVER-MIX. Over-mixing instantly activates the gluten in the flour, which results in a rubbery dough that shrinks during baking. From time to time stop the machine, scrape the sides and bottom of the bowl, then restart the machine to incorporate the crumbly mixture that separates from the dough and settles at the bottom.
Scrape the dough out of the bowl and press it into a ½-inch-thick rectangular block. Wrap airtight in plastic wrap and refrigerate overnight or for at least 2 to 3 hours (this is called “letting the dough rest”). After the dough is chilled it will be firm but it should still be pliable.
To Bake: For a 9-inch crust, remove the dough from the refrigerator, weigh it (you should have approximately 700 grams of dough), and cut it into 2 equal portions. Return 1 portion to the refrigerator. Following the instructions, roll the dough into a ¼-inch-thick circle and line a 9-inch tart pan or ring. Using a fork, perforate the bottom of the shell, making rows of little holes up and down the bottom of the dough with the tines of your fork. This step, called “docking,” is important, as it will allow steam to escape evenly. Refrigerate uncovered for at least 1 hour, or overnight if possible.
To pre-bake the dough (bakers call this “blind-baking”), preheat the oven to 325 ° F/ 160 ° C with the rack positioned in the middle of the oven (if you pre-bake the pastry on the lower setting the bottom will bake faster than the top). Crumple a piece of parchment paper, and line tart; fill all the way up to the edges of the tart with pie weights or beans. Bake with this “faux filling” for 15 minutes, then remove the faux filling and return the tart shell to the oven. Bake until golden brown and evenly colored, another 15 minutes or until golden brown. Remove from the oven and allow to cool completely before filling.