Preheat oven to 180 degrees C. Brush a 16 x 26cm (base measurement) slab tin with melted butter to lightly grease. Line the base and 2 long sides with non-stick baking paper, allowing the sides to overhang.
Base: Use a wooden spoon to combine the flour, coconut, sugar and butter in a large bowl. Use your hands to bring the dough together in the bowl. Transfer to the prepared slab tin. Use a metal spoon to press firmly over the base. Bake for 12 minutes or until light golden. Set aside to cool.
Passionfruit Top: Reduce oven temperature to 150 degrees C.Use a balloon whisk to whisk together the condensed milk, lemon juice and passionfruit pulp in a large bowl until smooth and well combined. Pour into the slab tin and spread evenly over the base. Bake in oven for 15 minutes until just firm to the touch. Set aside to cool completely. Cut into slices to serve.