Sift all the dry ingredients (flour, cocoa powder, baking powder, baking soda) together.
In a Mixing bowl, add oil and sugar. Whisk well. It should form foam.
Add egg, vanilla essence, buttermilk, warm water and whisk well.
Preheat the cooker for 10 min in high flame.
Now gently fold the dry ingredients into the wet ingredients.
Pour the mixture to the dusted pan.
Double tap the pan to release any air bubbles.
Place the pan in cooker and bake for 40 mins in low flame or until a toothpick comes out clean.
Remove the pan from cooker and rest it on wire rack.
Turn the pan upside into a plate and remove the cake from the pan.
Let it cool for few more mins.
You can frost with any frosting of your choice