Preheat oven to 160°C (320°F) with the fan function on for even heat distribution. If you don’t have a fan, adjust the temperature accordingly. Grease and line two 8-inch cake tins or use homemade cake release for easy removal.
In a bowl, sift together flour, cornflour, cocoa powder, baking soda, baking powder, and salt. Use a whisk or fork to mix until well combined, then set aside.
In another bowl, beat butter, vegetable oil, and sugar using an electric mixer. Whether you use a hand mixer or stand mixer, cream the mixture for 2-3 minutes until light and creamy.
Add eggs one by one, ensuring mixing between each for 10-15 seconds. Then, blend in vanilla, vinegar, and red liquid food color until well combined. Set the mixer aside for the next step.
Gradually add premixed dry ingredients to the wet mixture, folding gently by hand using a spatula until just combined. Pour in buttermilk, fold it in, and add the remaining dry ingredients. Do not overmix to maintain a soft texture.
Distribute the batter evenly between the two prepared tins. Bake for 30 minutes or until a toothpick comes out clean when inserted in the center.
Avoid opening the oven door too soon to prevent cakes from sinking. Also, watch the baking time to avoid overbaking, which can dry out the cake layers.
Once baked, allow the cakes to cool in the tins for 15-20 minutes before transferring to a wire rack. Let them completely cool before applying frosting, such as cream cheese buttercream frosting, for the best results.