Ingredients:

  • 1 cup (120g) all-purpose flour
  • 1 ½ cups (300g) granulated sugar, divided
  • ½ teaspoon salt
  • 1 cup (240ml) egg whites (about 8 large eggs)
  • 1 teaspoon vanilla extract
  • ¼ teaspoon cream of tartar
  • 1 ¾ cups (220g) all-purpose flour
  • 1 ½ cups (300g) granulated sugar
  • ¾ cup (65g) unsweetened cocoa powder
  • 1 ½ teaspoons baking powder
  • 1 ½ teaspoons baking soda
  • ½ teaspoon salt
  • 1 cup (240ml) buttermilk
  • ½ cup (120ml) vegetable oil
  • 2 large eggs
  • 2 teaspoons vanilla extract
  • 1 cup (240ml) boiling water

Instructions:

  1. Grease and line the bottom of a 9x13-inch sheet pan with parchment paper.
  2. Sift together flour, ¾ cup sugar, and salt in a bowl.
  3. In a large mixing bowl, beat egg whites with cream of tartar until soft peaks form.
  4. Continue beating while gradually adding remaining ¾ cup sugar until stiff peaks form. Mix in vanilla.
  5. Gently fold dry ingredients into whipped egg whites until just combined. Avoid overmixing.
  6. In another bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt.
  7. In a separate bowl, combine buttermilk, oil, eggs, and vanilla, followed by boiling water.
  8. Gradually add wet ingredients to the dry mixture until just combined.
  9. Pour angel food batter into one half of the prepared pan and devils food batter into the other half.
  10. Bake in a preheated oven at 350°F (175°C) for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
  11. Allow to cool in the pan for 10 minutes, then remove from the pan and cool completely on a wire rack before slicing.