Preheat the oven to 350 degrees Fahrenheit (180 degrees Celsius).
Grease muffin tins and line them with the paper cups.
Whisk together cake flour, baking powder, baking soda, salt en cinnamon.
In a second bowl whisk together the bananas, buttermilk and vanilla.
In a third bowl mix on medium speed the butter with the brown sugar until it's fluffy
Add eggs, one at a time, while beating until it's incorporated.
Reduce to low speed. Add half of the flour, then the banana mixture and end with the rest of the flour. Beat just enough to incorporate it.
Divide the mixture into the cups.
Bake for 20 minutes in the oven, and remind to turn the cake tin halfway of the time.
Let them cool down for 3 minutes and get them out of the tins.
Let them further cool down to room temperature on a wire rack (before putting the caramel butter cream on top.)
Caramel butter cream
Combine ¼ cup of sugar plus 1 tablespoon and the water in a heavy saucepan.
Heat over medium, until the sugar is dissolved and you have a clear syrup.
Cook until it comes to a boil and let it boil until it has got a very dark amber colour.
Remove from heat, put gloves on (for hot spatter) and add the cream, while stirring with a wooden spoon. Let cool down.
With a mixer, medium-high speed, beat the butter until fluffy.
Combine in a second bowl ¼ cup of the sugar with the egg whites.
Put the bowl over a pan of simmering water (au-bain-Marie) and whisk constantly until the sugar has completely dissolved.
Get it off the heat and mix further, starting on low speed gradually going to high speed, until peaks have formed. Change the speed of the mixer to medium and add the beaten butter in 3 times. Mix well after each addition.
Add the vanilla.
Set the mixer on low speed and very slowly add your caramel to the mixture.
Put the cream in a piping bag and make swirls on top of your cupcakes