Preheat oven to 175°C.
Line a muffin tin with paper liners.
In a bowl mix together flour, sugar, baking soda, salt and cocoa powder.
Make a well in the centre and add oil, water, apple cider vinegar and vanilla essence.
Mix until all the ingredients are incorporated.
Now fill 2/3rd of each liner with the batter and bake for 15-20 minutes or until a tooth pick inserted comes out clean.
Cool on wire rack.
Decorate with butter cream or serve as it is.