Pre-heat oven to 350°F (180°C).
Peel the bananas and place them in a food processor or high-speed blender. Blitz until smooth.
Add in the egg, oil and xylitol, then mix again. Next, add in the flours and baking powder, and blitz until a smooth batter is formed.
Transfer the batter into a greased or silicon cake tray. Place the halved strawberries on top and bake for around 60 minutes, until the cake is golden brown and cooked through.