Step 1

Preheat oven to 170°C (not fan-forced) and grease a 900ml loaf pan.

Step 2

Beat butter and sugar in a bowl using electric beaters until thick and fluffy.

Step 3

Add egg and beat until well combined.

Step 4

Add banana, yoghurt and vanilla extract and stir. Sift together flour, baking powder and cinnamon and fold through batter. Stir in walnuts if using. Pour into pan and bake for 1 hour or until a skewer inserted in centre comes out clean. Cool in pan for 10 minutes, then turn onto a rack to cool completely. Serve buttered, if desired.