Preheat your oven to 350°F (175°C). Grease and flour your 9-inch round cake pans, or line them with parchment paper for easy removal.
In a large mixing bowl, cream together 1/2 cup of unsalted butter and 1 1/2 cups of caster sugar until light and fluffy (about 3-5 minutes).
Add 2 large eggs one at a time, mixing well after each addition. Then, mix in 1/4 cup of cooking oil until everything is well combined.
Stir in 1 tablespoon of unsweetened cocoa powder and 2 1/2 tablespoons of red food coloring until fully combined. The mixture should be a rich red color.
Add 2 teaspoons of pure vanilla extract and 1 tablespoon of white vinegar. Mix until fully incorporated.
In a separate bowl, sift together 2 1/2 cups of plain cake flour, 1 teaspoon of baking soda, and 1 teaspoon of salt. Gradually add this to the wet mixture, alternating with 1 cup of buttermilk. Begin and end with the flour mixture, mixing until just combined.
Divide the batter evenly between the prepared cake pans. Bake in the preheated oven for 25-30 minutes or until a toothpick inserted into the center comes out clean.
Remove the cakes from the oven and let them cool in the pans for about 10 minutes before transferring them to a cooling rack to cool completely.