Preheat oven to 350 F. Line a 9"x13" pan with foil and spray with non stick cooking spray (this make removing from the pan and cutting SO much easier).

For the crust - cream the powdered sugar and softened butter together. Slowly add flour, 1/2 cup at a time, until fully integrated. The dough will be thick.

Dump dough into prepared pan and spread evenly along the bottom of the pan. The dough isn't very sticky, so I just used my fingers to spread the dough out.

Bake in 350 F oven for 15-20. When it starts to brown ever so slightly on the edges, you know its done. Do not let the top brown at all.

While the crust is baking, mix together the filling.

Mix granulated sugar, eggs, lemon juice and extract together with electric mixer. Sprinkle baking powder into filling and mix until just blended (don't over mix).

As soon as you remove the crust from the oven, pour the lemon filling on top of the crust.

Bake for another 15-20 minutes. You will know this is done when the top is no longer "jiggly". Once the top starts to brown a little, its time to take it out.

Let cool completely. Remove the Lemon Bars from the pan and cut into squares. These are best served within a day or two of baking.