Preheat your oven to 350 degrees.
Cut the butter into pats and place in a bowl for melting. It should be mostly-melted, with mostly liquid and some very soft pat pieces. You can melt using the microwave at 30 seconds at a time, or a double broiler method over a stove top.
To the butter, add the sugar, salt pure vanilla extract. Stir to combine.
Pour this mixture on top of the measured flour.
Combine everything together. It will be a bit crumbly but is easy to bring together.
Prepare a baking pan or surface with parchment paper. Pour the shortbread dough and form it evenly to the bottom. Use a inverted spatula and apply pressure so that it's smooth and even.
The shortbread will want to rise up and distort from being level while baking. To avoid this, poke holes evenly and throughout the top of the shortbread, using a toothpick or fork
Bake for 10-15 minutes so that there is a golden color at the corners and at the bottom. A little more or less time will be needed, depending on how thick or thin you lay down the crust. Allow to cool before adding filling or topping. Cut with a sharp knife and serve.