Preheat the oven to 180C/350F/Gas Mark 4 for 15 minutes. Lightly grease a 9×13 inch pan and line it with parchment paper.
In a large bowl, sift together the flour, baking powder, baking soda and salt. Mix in the sugar.
Make a well in the centre of the dry ingredients and stir in the wet ingredients one by one. Stir the mixture together using a whisk. Some lumps are okay.
Pour the batter into the prepared pan. Tap the pan to even it out and break any air bubbles.
Bake for 25-30 minutes or till golden colour.
Transfer the pan to a cooling rack and remove the cake after 15-20 minutes.
Place the cake on the rack for it to cool down completely before slicing it into 24 pieces.