The original idea for this cake was to fuse the white forest cake and the passion cake and make a passion forest cake. I'd planned to make a sponge cake and a passion fruit syrup and put them together to make a 'passion forrest' cake. But the ingredients for the passion fruit cake were so interesting I could not resist just to see how the final cake would taste like. I used whipped cream dressing as opposed to the cream cheese dressing which is ideal for this type of cake.  The cake tasted authentically passion fruity, the lemon and sour cream idea i think was the trick.
I still intend to try the 'passion forest' with the sponge cake, passion fruit syrup and cream cheese dressing. This recipe however is really good if you want a fully passion fruit cake, especially if you retain the dressing recommended in the recipe.