Preheat the oven to 350℉/180℃, and grease a 9x5 inch/23x13 cm loaf pan.
In a large mixing bowl sift together 180 g flour, 1 teaspoon baking soda, 1 teaspoon cinnamon powder and ¼ teaspoon salt.
Separately in a medium bowl, cream together 110 g butter, 100 g white sugar and 110 g brown sugar. To this add 390 g ripe brown bananas (mashed), 2 eggs, ½ teaspoon vanilla and mix till fully combined.
Fold the flour into the egg mixture till just incorporated, taking care not to over-mix (see notes).
Spoon the mixture into the tin and bake for 55-65 minutes or till a skewer inserted into the middle comes out clean. You may need to cover with parchment paper in the last 10 minutes to prevent the top browning too much.
Allow the bread to cool for 10 minutes before turning it out onto a cooling rack.
Notes
Soft, ripe, brown bananas are sweeter, have a stronger flavour, and impart more moisture compared with yellow bananas.Quickly ripen bananas - keep in the freezer for a couple of hours then leave them out on the counter to thaw before using. Note: banana skin will darken when frozen.Stir the flour in to the mixture gently using a wooden spoon till just combined - do not over mix or too much gluten will be released making the bread tough and too dense.Insert a clean skewer into the middle of the banana loaf and if it comes out clean its done.