Preheat oven for 180 degree C. 0.
Take egg, sugar and vanilla in a bowl and whisk well.
Add in buttermilk, oil and mix well.
Add in flour, baking powder, baking soda and salt. Fold gently.
Add in banana and raisin and fold gently.
Scoop it in a greased muffin pan till it is filled to the top of the mould.
Pop it in oven and bake for 20 to 25 mins.
Remove it and cool it down.