Preheat oven to 300 degrees. Line a 9x9 baking pan with parchment and set aside.
In a small bowl, combine the all-purpose flour, whole wheat pastry flour, and salt. Set aside. Cream the butter and granulated sugar for the cookie bars together. This should only take a minute. Add in your egg, vanilla, almond extract, and lemon zest. Mix to combine. Add in your flour mixture and again, mix to combine.
Put it into your parchment-lined pan and press to even out.
Place in the oven and bake for about 18 minutes. These should not be baked until they are browned, you will overbake them. Mine was baked to VERY, VERY lightly browned just around the edges.
Remove from the oven and allow it to cool for 5 minutes. Then, using the parchment paper, remove it from the pan and set it on a cooling rack. Cool them for another 25-30 minutes.
While they are cooling, mix your icing. I add all the ingredients with about 1 tablespoon of fresh lemon juice. Mix well and add more lemon juice to get the consistency you are looking for. Mine was a little stiff, but you can always make it a little thinner if you want.
These are delicious served right away, but they also hold really well in the refrigerator for up to 3 days! Just make sure they are wrapped well or stored in an airtight container.