The Real Red Velvet Cake

Ingredients

• Cooking spray
• 1 ½ cups all-purpose flour
• 1 ½ cups cake flour
• ½ cup cocoa powder
• 1 ½ teaspoons baking soda
• ½ teaspoon kosher salt
• 1 ½ cups buttermilk
• 2 teaspoons vanilla extract
• 3 ¾ cups brown sugar
• 1 ½ sticks unsalted butter, softened
• 3 large eggs, at room temperature
• 1 cup white sugar
• 1 cup whole milk
• ½ cup all-purpose flour, sifted
• ½ teaspoon salt
• 2 cups unsalted butter, softened
• 1 ½ teaspoons vanilla extract