Mix flour and light brown sugar using a food processor until fully incorporated. Toss butter into flour mixture and pulse to combine using short bursts of power until butter is cut into tiny pea-sized pieces and dough appears lumpy. Sprinkle crust mixture into an ungreased 13x9x2-inch baking pan as evenly as possible, press down to create a packed surface.
Place pan in middle of oven and bake until golden, approximately 20 minutes.
Lemon Topping
Beat eggs in a medium bowl with an electric mixer until well blended. Add vanilla extract and 3/4 cup of powdered sugar; mix well. Add lemon juice and remaining powdered sugar. Mix until powdered sugar is completely dissolved. Add zest (optional).
As soon as crust is finished, remove from oven and reduce oven temperature to 300˚F. Immediately pour lemon mixture over hot crust. Bake completely, about 20-30 minutes.
Cool and cut into 24 bars. Yields 1 bar per serving.
Notes
-The crust must be HOT when you pour on the lemon mixture. -Approximately three lemons to yield the amount of juice and zest in this recipe. -WW Points Plus Value: 3.