Red Velvet Chocolate Cake

INGREDIENTS

• Unsalted butter, for cake pans
• 2 1/2 cups cake flour, not self-rising
• 1 teaspoon salt
• 1/4 cup cocoa powder
• 1 1/2 cups sugar
• 1 1/2 cups canola oil
• 2 large eggs
• 1/4 cup red food coloring
• 1 teaspoon pure vanilla extract
• 1 cup buttermilk
• 1 1/2 teaspoons baking soda
• 2 teaspoons white vinegar
• Seven-Minute Frosting