Preheat the oven to 170C.

Put the flour, baking powder, and baking soda in a bowl, and combine well.

In another bowl, mix the melted butter and sugar and beat until blended.

Whisk the eggs one at a time and add in vanilla essence.

Add mashed bananas and stir in drained sultanas.

Add in half of the flour mix and stir well.

Mix in the yogurt/sour cream and the remaining of the flour mix.

Stir well and pour into a 22 cm loaf tin and bake for about an hour or till the cake is golden.