To make the sponge: Preheat the oven to 350 degrees F.
Grease and line 2 (8-inch) cake pans with parchment.
In a medium bowl, mix the flour, baking powder with the cornstarch and sift the ingredients together twice. Beat the eggs with the sugar for about 7 to 8 minutes or until the mixture is pale and thick. Gently fold the flour mixture into the beaten eggs.
Mix the butter with the boiling water, and then add it to the sponge batter, stirring gently. Divide the mixture between the prepared cake pans, and bake for 20 minutes or until the cakes are golden brown and separating from the tins. Remove the pans from the oven. Cool the sponges in the pans for 10 minutes before turning them out onto a wire rack to cool completely.
To make the icing: While the cakes cook and cool, beat together the sugar, butter and passion fruit pulp until a spreading consistency is reached.
To serve, place 1 of the cakes on a serving plate and spread it with the whipped cream. Layer on the remaining cake and spread that with the passion fruit icing.