Preheat the oven to 170ºC/325ºF/gas 5. Grease a 1.5 litre loaf tin with dairy-free margarine and line with greaseproof paper.
Sieve the flour into a food processor, then add all the remaining ingredients (except the bananas). Blitz well until combined. Peel the bananas, roughly mash in a bowl, then add to the food processor. Pulse briefly to combine, then scrape the mixture into the prepared loaf tin.
Place the tin in the hot oven and bake for 50 to 55 minutes, or until golden and an inserted skewer comes out clean. Leave to cool slightly in the tin, then turn it out onto a wire rack to cool completely. Enjoy with a drizzle of honey and a few extra slice of banana, if you like.