Preheat the oven to 350°F for a metal pan or 325°F for glass.
Line a 9x9 baking dish with parchment paper, making sure the edges of the paper hang over the edges of the pan.
For the shortbread layer, beat together 1/2 cup butter and 1/2 cup sugar in a large bowl. Add both eggs and 1 tsp vanilla and beat until well combined.
Add 1 1/2 cups of flour and 1/2 tsp salt and mix until combined.
Scrape dough into the pan and press with your fingertips in an even layer.
Spread the pie filling over the top of the crust. (see variations for homemade apple layer)
Make the streusel topping by whisking together the brown sugar and remaining flour.
Cut in the butter using a pastry blender or fork until the mixture resembles coarse sand.
Sprinkle the topping over the pie filling.
Bake in the preheated oven for 35 minutes or until done. If using a glass pan, check for doneness after about 25 minutes.
The pie bars are finished baking when the filling is bubbling and the streusel topping is golden brown.
Allow the bars to cool completely, then remove them from the pan by pulling the edges of the parchment paper up.
Cut into bars before serving.
Enjoy!
Notes
If using fresh apples, see variations in post for ideas. Nutrition info below is calculated based on canned apples.