Oven 170 C / 350 F deg, to bake the cake / 8 inch cake tin - 20 cm. 200 C / 180 F to bake the sweet potato
Put the flour, baking powder and sugar in a bowl with the cocoa powder.
Add the water, vanilla, oil and vinegar. Mix until a smooth batter is formed
Pour into a lined round tin. Bake gently for 30-40 minutes or until cooked in the centre when tested with a toothpick. If you have a hot oven bake at 160 C.