Step 1 – Preheat oven to 180°C/160°C fan-forced. Line a 12-hole 1/3 cup-capacity muffin pan with paper cases.
Step 2 – Sift flour and baking powder into a large bowl. Add caster sugar. Stir to combine. Combine banana, spread, milk and vanilla in a large jug. Add to flour mixture. Stir until smooth.
Step 3 – Spoon mixture into cases. Bake for 18 minutes or until golden and a skewer inserted in centre of 1 comes out clean. Stand in pan for 5 minutes. Turn out onto a wire rack to cool completely.
Step 4 – Make icing: Place icing sugar, passionfruit pulp and 1 to 2 teaspoons hot water in a bowl. Stir until icing is smooth and spreadable. Spread cupcake tops with icing. Top with lemon zest (if using). Serve.