Cream the butter and powdered sugar together until smooth.
Disolve the salt into the egg, then add to the butter mixture. Mix until combined. Be sure to scrape down the sides of the bowl, so you won't have chunks of butter later on. It may looked curddled, that's okay.
Add the flour, then mix until just combined.
Dump out onto a clean working space. With the palm of your hand, push the mixture away from you and against the worktop. Repeat 2-3 times.
Pull the dough back together and repeat the process 2-3 times. The goal of this is to create a smooth dough, without any hidden chunks of butter or flour lumps.
Pull into a ball, wrap in plastic wrap and let chill in the fridge for at least 30 minutes
After the dough has chilled, rolled out into a circle about two finger widths larger than your pan. Trim excess dough.
Roll the dough up on your rolling pin and transfer to the pan. Start working the dough into the corners of the pan, then trim the excess dough from the top of the pan using a paring knife.
Dock the dough, then cool in the freezer for 15 minutes
Preheat the oven to 180°C (350°F). Bake the tart crust for 20 minutes or until golden brown. Check on the crust about half way through baking. If you noticed that the center has domed, poke it with a fork so you have a flat bottom.
Let cool for 30 minutes.