You will need
75g softened butter
110g unrefined (golden) caster sugar
1 large beaten egg
225g plain flour
2 level tsp baking powder
grated rind of 1 orange and 1 lemon (optional)
4 ripe bananas
50g chopped walnuts
Grease and line a 8.5x19cm loaf tin, or set 12 paper muffin cases into a muffin tin. Heat the oven to 350F/180C/Gas mark 4.
Put the butter, sugar and egg into a bowl, and sift in the flour and baking powder. Using an electric mixer, whisk until thoroughly combined. Add the grated orange and lemon rind if using.
Slice the bananas into another bowl, and mash to a pulp. Add to the flour mixture along with the walnuts and whisk again thoroughly.
Spoon the mixture into the tin or cases and bake until risen and browned, and springs back when pressed. A loaf takes about 50 mins and muffins take 15-20 mins.
Leave cake to cool in the tin for 10 minutes before trning onto a wire tray.