In a medium bowl, beat the butter until creamy. Add the granulated sugar to the butter and continue to beat until combined completely. Add the 2 tablespoons of flour and mix until everything resembles course crumbs (sort of the consistency of bread crumbs).
Press the crumb mixture into an ungreased square pan (8x8x2). Bake at 350° for about 15-20 minutes until set and light golden brown
Make the filling
While the crust is baking. Mix all of the filling ingredients in a medium bowl until well combined (about 2 minutes).
Assemble
Once the crust is done baking, remove it from the oven and carefully pour the filling over it. Return to the oven for another 20 minutes. When done, the edges will be light brown and the center will be set.
Let cool completely then cut into 16 bars. Sift powdered sugar over the top if desired.