In a large bowl, use two knives (or a pastry cutter) to combine the flour and butter until crumbly. Press into the bottom of a 9x13-inch pan. Bake about 25 minutes, until the crust is golden. Remove from the oven and cool.
In a medium bowl, use an electric mixer to combine the cream cheese and sugar. Spread evenly over the cooled crust.
In another medium-bowl, whisk together the milk and lemon pudding mix for about 4 minutes, until thickened. Spread over the cream cheese layer. Chill in the fridge until set, at least 30 minutes. Top with the Cool Whip, and serve.