Preheat the oven to 325°F (163ºC). Prepare a 9×13 metal baking pan by spraying the sides with baking spray and lining the bottom with parchment paper.
In a medium bowl, whisk together the sifted cake flour, cocoa powder, baking soda, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment (or with a hand mixer and large bowl), cream the butter on high for two minutes, then add the vegetable oil and sugar. Cream together on medium-high until pale and fluffy, about 2 minutes. Scrape down the bowl and paddle. Turn the mixer to low and add the eggs one at a time. Once the eggs are incorporated, add the vanilla and white vinegar and mix on low for another 30 seconds. Scrape down the bowl and paddle once more.
Mix the red food coloring into the buttermilk. With the mixer on low speed, alternate adding the flour mixture and buttermilk in three additions, beginning and ending with the flour mixture. Mix only until the ingredients start to come together, then whisk the batter by hand a few times to make sure there are no large lumps.
Pour the batter into the prepared pan and bake for 30-35 minutes, until a toothpick inserted comes out clean. Allow the cake to cool completely before frosting, either in the pan or gently invert it onto a cooling rack or serving plate to cool.