Preheat the oven to 175 °C. Grease and line a 2 lb/900g loaf tin with baking parchment or a pre-cut loaf tin liner.
In a medium bowl, sieve together the plain white flour, baking powder, bicarbonate of soda, ground cinnamon and salt. Whisk together until well combined.
275 g plain white flour, 1 teaspoon baking powder, ½ teaspoon bicarbonate of soda, 1 teaspoon ground cinnamon, ¼ teaspoon salt
In a separate medium bowl, combine the vegan yoghurt, soy milk, vinegar and vanilla extract. Whisk until smooth then add the dark brown sugar & sunflower oil. Whisk until smooth.
60 g vegan yoghurt, 2 tablespoon soy milk, 1 teaspoon white vinegar, 1 teaspoon vanilla extract, 150 g dark brown soft sugar, 130 g sunflower oil
In a third medium bowl, mash two of the three bananas as smoothly as possible then add to the bowl with the other wet ingredients. Whisk together until smooth.
3 bananas
Add the wet ingredients to the dry ingredients and mix until just combined. Add the batter to the prepared loaf tin. Peel the final banana and slice in half length-ways. Lay both halves on top of the banana bread batter in the loaf tin and push in gently. Finally, sprinkle the top of the batter and halved banana with the demerara sugar then place in the oven to bake for 55 minutes.
2 tablespoon demerara sugar
Remove from the oven and leave to cool to room temperature before slicing and serving. If you have leftovers the next day, slice and toast the banana bread then serve with vegan butter, vegan yoghurt or maple syrup.
Notes
1. Be sure to choose a vegan yoghurt which is unflavoured and unsweetened. Same goes for the soy milk. You don't want anything to take away from that gorgeous banana flavour. 2. Don't worry about mashing your bananas to absolute pure smoothness. I've found that a slightly lumpy banana bread batter actually results in a higher rise but still with a nice even crumb and moist texture. 3. If you don't have demerara sugar you can use granulated sugar instead.