Preheat the oven to 180C | Gas mark 4. Line a loaf tin with baking parchment and set aside.
Add the flour, sugar, baking powder and salt into a large mixing bowl and stir to combine.
Pour the sourdough starter over the flour together with the melted vegan margarine and two mashed bananas. Using a wooden spoon mix to form a thick, smooth batter.
Scrape the batter into the lined loaf tin. Place in the middle of the oven and bake for around 60 inutes until a toothpick inserted in the centre of the loaf comes out clean.
Let it cool completely on a wire rack before cutting into slices.
