Preheat your oven to 180°C (350°F). Line a 23cm round cake pan with parchment paper and set aside.
In a large mixing bowl, sift together the cake flour, cocoa powder, baking soda, and salt. This ensures an even distribution of dry ingredients and a smooth batter.
In your stand mixer, beat the vegetable oil and sugar on medium speed until the mixture is pale, fluffy, and smells slightly sweet, about 2-3 minutes.
Add eggs one at a time, beating well after each addition, until the batter is smooth and slightly thickened.
Mix in the vanilla extract and red gel food coloring, watching the batter turn a vivid crimson as you blend.
In a separate bowl, whisk together the buttermilk and white vinegar until combined.
Gradually add the dry ingredients to the wet mixture in three additions, alternating with the buttermilk mixture. Mix on low speed just until combined after each addition, avoiding overmixing to keep the cake tender.
Pour the batter into the prepared cake pan, smoothing the top with a spatula for an even surface.
Bake in the preheated oven for 25-30 minutes, until a toothpick inserted in the center comes out clean and the edges are slightly pulled away from the pan.
Remove the cake from the oven and let it cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. The cake should be deep crimson with a moist, tender crumb.
Once cooled, frost with your favorite cream cheese or vanilla frosting and enjoy this striking, velvety cake.
