Preheat oven to 350

Mix flour, margarine, powdered sugar and vanilla extract thoroughly in a small bowl.

In an ungreased 8x8x2 pan, press the dough evenly with hands (If dough is sticky, flour fingers).

Bake for 20 minutes.

Beat the lemon mixture ingredients in a medium bowl on medium speed until light and fluffy.

When crust is done, pour lemon mixture onto the hot crust.

Bake for 25 minutes (or until there is no indentation when touched lightly in the center).

Sprinkle the top with powdered sugar (optional)

Let stand until cool. Cut into 1 1/2 inch squares.