Preheat oven to 300 degrees and liberally grease a 10-inch tart pan with a removable bottom with butter.
Add the butter to the large bowl of a stand mixer and beat on medium-high for 3 minutes with the paddle attachment. Add vanilla and mix in. Add confectioner's sugar and beat for another 2 minutes until light and fluffy.
Sift flour and salt, and gradually add the mix to the butter until it is just blended. Do not overmix.
Turn the dough into the pan. Put plastic wrap over the dough and press evenly into the pan.
Keep the plastic wrap on the dough and chill in the refrigerator for 20 minutes.
Remove from the refrigerator, score into 8 sections, prick all over with a skewer, and sprinkle with sanding sugar.
Bake for 1 hour. Checking several times. Remove to a wire cooling rack. Cool completely. Remove the side of the pan and cut along scored lines. Remove the bottom of the pan. Enjoy.