Measure the butter and salt into the bowl of a stand mixer. Fit mixer with paddle attachment.
Sift then measure the powdered sugar, almond flour and all purpose flour into separate bowls and set aside.
Crack the egg, and mix with a fork to combine the yolk and white. Measure out 63g. Add a tsp or two more of water to get to 63g if necessary - eggs vary in size.
Mix the butter on LOW speed to incorporate the salt. Take care to mix on low so as to not incorporate air into the butter, as this will cause cracks and bubbling of your crust. Stop the mixer, scrape down the paddle and bowl sides and bottom.
Add the powdered sugar, and mix again for a minute on low. Scrape the bowl and paddle. Add the almond flour, mix again for a minute on low, and scrape the bowl and paddle.
With the mixer on low, add the egg gradually. Mix for a moment to incorporate, then stop and scrape everything down again. Add ⅓ of the flour and mix on low. Add the remaining flour, and mix just until everything is combined.
Finish mixing and scraping the bowl by hand with the spatula, making sure all the flour is incorporated.
Scrape out the dough onto a sheet of plastic wrap. Cover the dough, then use your hands too quickly and gently form into a disc shape that is ½” to 1” thick. Wrap thoroughly, and place in the fridge for at least 8 hours. Dough may be frozen for a few months, if tightly wrapped and placed into a freezer-safe ziplock back or other container with minimal headspace to prevent moisture loss (freezer burn).
To roll, allow refrigerated dough to come to room temperature for 5-10 minutes (taking care if your kitchen is hot - the dough will become hard to manage). Whack the wrapped disc of dough a few times across both sides to help loosen up the structure. If you notice a lot of cracking, let the dough sit for a moment before proceeding
Lightly dust a surface large enough to roll with flour. Unwrap the dough, and place on the floured area.
Using a firm motion, starting from the center of the dough disc, roll directly away from you. Gently pick up the dough, just enough to slide and move it, and rotate it ¼ turn. Repeat this process, adding more flour as needed to the counter and the rolling pin to prevent sticking, until you reach ¼” thickness. Be sure to apply smooth and even pressure. Take care to not lift up or press down more at the edge of the dough - that will result in edges that are too thick or too thin.
If you are new to rolling out doughs, I suggest to roll out the dough on a piece of parchment OR a silpat (silicone mat). You can then transfer your dough to the fridge at any time if the dough starts to heat up too much, and stick. This is better than adding more flour. Allow the dough to rest for 5 minutes in the fridge, then transfer the parchment sheet or silpat with the dough back onto the counter, and return to the rolling and turning process.
To transfer into the tart ring, gently roll-up the dough onto the rolling pin, and lay into the tart ring. This can be tricky to center - but you can gently move the dough once it is draped in the ring - and patch if tearing occurs.
Gently hold the edge of the dough with one hand, and with the other gently fit the dough into the corner of the tart ring. Work your way around the pan, allowing the excess to hang over the edge of the ring. If rips or tears happen, patch them up with the excess dough.
Using your fingers, gently press off against the side of the pan the extra dough. Go around the pan one time to make sure the sides of the dough are flush to the tart ring edge, and into the corner of the tart ring. I like to use a measuring cup edge to gently press into the edges to make sure they are flush to the pan. Poke the pastry bottom and sides with a fork (docking) to help steam escape as the tart shell bakes.
Transfer the pastry shell onto a baking sheet, and into the fridge for at least 2 hours and up to overnight, uncovered.
Blind Bake: line the refrigerated tart with aluminum foil or parchment paper, making sure to fit the foil or paper flush onto the dough. Fill with dried beans or rice. Bake in the middle rack of the oven at 325F for 15 minutes. After 15 minutes, gently remove the foil/paper with weights, and return to the oven to finish baking for another 15 minutes. The shell should be golden brown, and should be firm to the touch. Depending on your oven you may need to subtract or add time - watching towards the end of baking until you know your timing is not a bad idea! Remove from the oven and allow to cool completely before filling.
The tart will pull away from the sides of the pan as it cools, enabling you to remove it from the ring. If you are using a false-bottom tart pan, you can leave the bottom on during serving, if desired. To remove the ring from the bottom, carefully lift the tart pan (holding the sides of the ring) and place on a can or small bowl, and allow the ring to drop from the tart shell sides (I find that you can do this before or after filling - it is slightly less precarious before filling!). Once cooled, you can wrap to help maintain freshness or leave on the cooling rack if your kitchen is not humid.