Mix butter, sugar, water, cocoa & vanilla in pot on low fire

When it metls, keep a cup of the sauce on the side which would be used as the sauce for the cake in the end

Add the mixture to flour, eggs & baking powder. Mix well

Add some butter and flour on the edges of the cake pan so that the cake doesn't stick

Pour the mixture in the cake pan, then in the oven for 15-20 minutes

After the cake cools down add the sauce from step 2 on top of the cake