In a large mixing bowl, combine flour and confectioner's sugar, stir just to combine. Using a pastry blender, cut butter into flour until it resembles pie crust dough. Press dough into the bottom of an ungreased 9 x 13 pan. Bake crust in a preheated 350 degree oven for 18-20 minutes, just until edges start to turn golden.

While crust is baking, prepare filling. Whisk together filling ingredients until smooth and a foam begins to form on top. Let filling rest.

When crust is done baking, remove from oven. Stir filling to blend foam back in then pour over baked crust. Bake again for 20 minutes, or until top turns golden brown.

Let cool completely. Sprinkle with powdered sugar just before serving.

Notes

Tip. Dip knife in water before cutting for a cleaner cut.

adapted from All Recipes