Pre-heat oven to 325F (160C), lightly grease and flour an 8 inch (20 cm) square cake pan.
In a medium bowl whisk together the flour and salt. Set aside.
In a large bowl cream the butter on medium speed, then add the sugar and beat together. Add the whisked flour and combine well. Spread evenly on the prepared pan and bake for 5 mintues.
Raise the heat to 350F (180C).
APPLE PIE FILLING
While the base is baking, mix together the chopped apples, flour, brown sugar and cinnamon. Spoon evenly on the shortbread base.
In a medium bowl mix together the flour, brown sugar and cinnamon, cut in the cold butter until you have coarse crumbs, then gently stir in the nuts. Sprinkle evenly over the apple pie filling. Bake for approximately 40-45 minutes or until the apples are tender. If the top starts to brown too much, then cover with foil and continue to bake. Enjoy!