Banana Sheet Cake

Preheat the oven to 180 °C fan (200 °C conventional).

Line a baking sheet with parchment paper.

Peel the ripe bananas and mash them with a fork into a smooth puree.

Beat the soft butter, sugar, cinnamon and egg in a bowl with a hand mixer until fluffy.

Stir the banana puree and the chopped walnuts into the butter-and-egg mixture.

Mix the flour and baking powder in a separate bowl.

Fold the flour–baking powder mixture into the batter gradually until a smooth batter forms.

Spread the batter evenly on the baking sheet.

Bake the cake for about 20 minutes until golden and a skewer comes out mostly clean.

Remove the banana sheet cake from the oven and let it cool completely on a wire rack.

Dust the cake lightly with powdered sugar, cut it into 20 pieces and place a banana slice and a walnut piece on each.