In an ungreased round, or 9x9 inch square or a 9x13inch lamington tray, add the plain flour, sugar, salt, and bicarbonate of soda.
Using a whisk or a fork, stir the ingredients together until they are somewhat blended.
Using a fork or spoon, make two small and one slightly larger depressions in the cake mix.
In the large depression, add the oil.
In one of the small depressions, add the vinegar.
In the other small depression, add the vanilla extract.
Gently pour the cold water over all of the ingredients.
Using the fork or whisk, gently stir the ingredients until they are fully combined. Make sure to mix in the mixture in the corners if using a square or rectangular pan.
Gently tap the pan on the countertop to smooth out the top and release any bubbles that may be in your mixture.
Bake for 25-30 minutes until a skewer comes out clean.
Remove from oven to cool completely before icing and serving.
Ice with your favourite icing, or sprinkle with icing sugar / powdered sugar.