Spray a 17x12 rimmed cookie sheet with non-stick spray.
In a large mixing bowl, cream the butter and sugar together until creamy.
Add in the eggs, vanilla and almond extracts, and then mix until well combined.
In a small bowl, whisk the flour, salt and baking powder together. Slowly add the dry ingredients into the wet ingredients. Mix just until the dough is well combined. Do not overmix!
Press the cookie dough evenly into the greased cookie sheet and bake for 15-20 minutes. (My oven took about 17 minutes. Try not to let the cookie bars brown. If the edges start to brown, remove from oven immediately.)
Cool the bars on a wire rack.
Make the Frosting
In a stand mixer bowl, with the mixer on medium speed, whip the butter for 2 minutes until it is almost white in color.
Add in the powdered sugar, vanilla and 3 tablespoons milk.
Beat on low speed for 3-5 minutes, adding in the last tablespoon of milk if the buttercream needs to be thinner.
Add in food coloring if you'd like and mix well.
Once the cookie bars are cool, frost the bars and decorate.
Store in an airtight container at room temperature.
The calories shown are based on the cookie bars being cut into 24 pieces, with all of the frosting used. 1 serving is 1 frosted cookie bar. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate.