Prepare a 9 x 13" baking pan by lining with parchment paper
Use a mixer to beat the butter, brown sugar, salt and vanilla until combined
Add the flour and continue mixing until incorporated. The dough will be crumbly, but will press evenly together.
With your hands, press the dough firmly and evenly into the bottom of the prepared pan.
Bake in centre of oven 15 minutes. Remove from oven and allow to cool while you make the filling
For the Filling
Using a mixer, beat eggs. Add sugar and beat, then butter, vanilla, flour, and salt.
Beat for a couple of minutes, then stir in pecans.
Spread filling evenly over crust
Return to oven and bake for 20-25 minutes or until filling is set. The top should be golden brown and the filling should still have a slight jiggle when you move the pan.
Allow to cool completely on a wire rack before removing from pan. Cut into squares
Notes
Have your butter soft at room temperature. I let it sit out overnight.For best results, have the eggs at room temperature as well. A stand mixer works well for both the crust and the filling, but you can also use a hand held eclectic mixer.Line your baking pan with parchment, leaving a couple of inches of overhang. This will make it easy to lift the uncut squares out of the pan. Use a knife first to loosen the sides.The crust should be completely cooled before spreading the filling on top.Make sure the butter tart bars are completely cool before slicing them.The squares will keep covered, at room temperature for a couple of days, otherwise, put them in the fridge for up to a week.To freeze: After slicing, flash freeze the bars on a tray until they are firm, then transfer them to an air tight container or bag. Freeze for up to three months.