Mix crust ingredients in a bowl. Press into an un-greased 15½" x 10½" x 1" baking pan. Bake for 14 to 16 minutes. Prick with a fork if it puffs up during baking. Remove from oven before it browns.
Mix cream cheese filling ingredients and pour over partially baked crust. Bake for 6 to 7 minutes, or until filling is slightly set. Remove from oven.
Mix lemon filling ingredients together, adding the lemon juice last. Slowly pour over the cream cheese filling. Bake for 14 to 16 minutes, or until filing is set. Filling may puff up during baking, but will fall when removed from oven.
Cool completely in pan before cutting into squares. Serve with a little powdered sugar overtop (optional)