Sift the flour and salt into a medium bowl and whisk together. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, oil, sugar, and vanilla on medium speed until well combined, about 5 minutes.
Add 1 tablespoon rose and 1/2 teaspoon red food coloring and beat until the batter is evenly colored. Scrape the sides and bottom of the bowl to make sure all the mixture is colored.
Add the eggs, two at a time, beating until each addition is incorporated before adding the next. Scrape down the sides of the bowl with a spatula when necessary.
Add the flour mixture in four parts, alternating with the buttermilk in three parts, beating just until each addition is incorporated before adding the next; do not overmix.
* Note: If you don’t have buttermilk, stir 2 teaspoons cider vinegar or distilled white vinegar into 2 cups room temperature whole milk and let stand for 10 to 15 minutes, until the milk has thickened slightly. *
In a small cup, combine the baking soda and vinegar. With the mixer running, immediately add the mixture to the batter. Beat for 10 seconds.
Scrape the batter into the prepared pan or pans and spread it so that it is smooth in the pan(s). Bake until a toothpick inserted in the center comes out clean, about 45 minutes for the 9 x 13-inch pan or 55 minutes for the 8-inch pans, rotating the pan(s) halfway through.
Transfer to a wire rack and let cool completely in the pan(s). Cover tightly with plastic wrap and refrigerate overnight. Loosen the edges with a straight spatula, invert the pan(s) to remove the cake, and peel off the parchment.