Step 1: Preheat your oven to 350°F (175°C). Line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides, and lightly grease any exposed pan surfaces.
Step 2: In a large mixing bowl or the bowl of a stand mixer, cream together the softened unsalted butter and granulated sugar for about 3 minutes until the mixture is light and fluffy.
Step 3: Beat in the egg, egg yolk, vanilla extract, and almond extract until well combined and smooth.
Step 4: In a separate medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Gradually add this dry mixture to the wet ingredients, mixing on low speed until just combined. Do not overmix.
Step 5: Transfer the cookie dough into your prepared baking pan. Using your hands or an offset spatula, press the dough evenly across the bottom of the pan.
Step 6: Bake for 16-20 minutes, or until the edges are lightly golden and a toothpick inserted into the center comes out clean. Avoid overbaking to keep the bars soft and chewy.
Step 7: Remove the pan from the oven and let the cookie bars cool completely on a wire rack before frosting.
Step 8: While the bars cool, prepare the strawberry frosting. In a clean mixing bowl, beat the room temperature unsalted butter with vanilla extract. Add the optional lemon juice and the finely crushed freeze-dried strawberries. Gradually add 3 cups of powdered sugar, beating until the frosting is smooth, creamy, and spreadable. Add more powdered sugar as needed to reach desired consistency.
Step 9: Once the cookie bars are completely cool, use the parchment paper overhang to lift them out of the pan. Spread the strawberry frosting evenly over the top. Garnish with fresh strawberry slices or colorful sprinkles if desired.