Preheat oven to 175 degrees celsius (fan-forced). Grease a round 23cm cake tin.
Mash the bananas with a fork and set aside.
Sift the plain flour, baking powder, bi-carbonate soda, cinnamon and salt together. Set aside.
Place the room temperature butter into a large bowl. Add the raw sugar and brown sugar. Use hand-held beaters or a stand mixer to beat on high speed for 4-5 minute or until pale, smooth and creamy.
Add the eggs, vanilla extract and bananas and beat on medium speed until combined.
Alternate adding the dry ingredients with the buttermilk and continue mixing on low until only just combined (it's fine for the mixture to be a little lumpy).
Pour the cake mixture into the prepared tin and bake for 45-50 minutes (see notes). The cake is ready when a skewer inserted into the middle comes out clean.
Remove the cake from the oven and leave in the baking tin for 15 minutes. Turn onto a wire rack to cool completely.
To make the cream cheese frosting, beat the room temperature cream cheese and butter on high speed until smooth, pale and creamy (approximately 3 minutes).
Add the sifted icing sugar and vanilla and mix on low speed, slowing increasing to high speed for 3 minutes. If the frosting is too thick, add up to a tablespoon of milk and beat through.
Spread the frosting over the cooled cake. Store in an airtight container in the fridge up to 3 days.
Thermomix Instructions - Click the link in the notes section below for the Thermomix recipe.