Preheat oven to 375 degrees.

 In a large mixing bowl, combine flour, baking powder, cinnamon and sugar.  

In a separate bowl, combine Nutella, banana, butter, buttermilk, egg and vanilla.

 Stir wet ingredients into dry just until combined.  

Spoon into greased muffin tins.  

Bake for 17-20 minutes or until a wooden pick inserted comes out clean.  

Remove from pan to wire rack.

Serve warm or at room temperature.