Prepare cake as directed in a 10" round cake pan or a 10" round springform pan.
Blend cream cheese, powdered sugar, and lemon juice together. In a medium bowl, whip heavy whipping cream to stiff peaks. Gently fold into cream cheese mixture and blend by hand. Chill until ready to add to the cake.
Mix flour and powdered sugar in a small bowl. Crumble butter in and dribble in vanilla extract. The crumbles should be no larger than pea-size. If you have trouble crumbling mixture, chill for a few minutes. Chill until needed.
After the cake is cooled, cut in half. Spread cream cheese mixture, saving 1/2 cup, on the bottom half and carefully place top layer back. Spread the rest of the cream cheese mixture on the sides of the cake. Press crumb topping into sides gently. (We only added it to the top)