Preheat your oven to 350 degrees. Prepare your ingredients and pan. Melt the butter pats until they are extremely soft and only mostly liquid. Add the melted butter, sugar and vanilla into a bowl and combine. Pour on to the top of the prepared dry ingredients.
Mix by hand with a spatula or spoon or with a machine, until all of the ingredients have come together and have literally lifted from the bowl, forming the shortbread dough.
I used a 7" x 11" rectangle tart pan. The dough will form a ball in your hands within seconds and is very pliable. You can use cooking spray or parchment paper for the bottom of your tart pan.
Push it down toward the bottom of the pan.
Work it to try to evenly cover the bottom of the pan. You can also use a inverted spatula to help get the base evenly distributed.
Form and arrange the dough to come up to the top and the sides.
For a nice and clean finish, push the excess dough away from the top edge of the pan. Use a fork or toothpick to poke holes at the bottom of the dough so that it does not rise during baking.
Bake until golden brown. Depending on the thickness and size of your crust, you'll want to start checking the bake at 10-15 minutes and it may take up to 20.
You can have this prepared in the refrigerator for up to 24 hours before you bake. Allow to completely cool before pouring in your fruit curd of choice.