Preheat the oven to 180C. Lightly grease a 20cm square cake pan then line the base with baking paper.
Beat the butter, caster sugar, eggs and vanilla essence in a large mixing bowl, until light and creamy. Sift in the flour and baking powder, mix well then fold in the passionfruit pulp. Spoon into the prepared pan and smooth the top. Bake for about 30 minutes, until golden. Cool for 10 minutes then turn out onto a cake rack to cool completely.
To make the icing, beat the icing sugar, butter and passionfruit pulp, until smooth. Spread over the cake. Cut into squares to serve. Best eaten fresh although it can be frozen.
Tip
The following bakes with seasonal fruit all use level metric measurements. For best results, when measuring a dry ingredient spoon it into the measuring cup then level the top with the spoon. Place the measuring cup on the bench to check if the level is correct. Do not pack it down. The exception to the rule is brown sugar. This should be lightly packed — except when the recipe states is should be ‘firmly’ packed.