Ingredients:

  • 2 cups (250g) all-purpose flour, plus more for dusting the pan
  • 1 ½ teaspoons baking powder
  • ¼ teaspoon baking soda
  • ½ teaspoon salt
  • ¾ cup (1 ½ sticks, 170g) unsalted butter, softened
  • 1 ¾ cups (350g) granulated sugar
  • 2 large eggs
  • 1 teaspoon vanilla extract
  • 1 cup (240ml) buttermilk
  • 2 tablespoons unsweetened cocoa powder
  • 2 tablespoons hot water

Instructions:

  1. Preheat oven to 350°F (175°C). Grease and flour a 9x5 inch loaf pan.
  2. Whisk together flour, baking powder, baking soda, and salt in a medium bowl.
  3. Cream together softened butter and granulated sugar until light and fluffy.
  4. Beat in eggs one at a time, then stir in vanilla extract.
  5. Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined – do not overmix.
  6. Divide the batter in half into two separate bowls.
  7. In a small bowl, whisk together cocoa powder and hot water until a smooth paste forms. Add this to one bowl of batter and mix until well combined.
  8. Spoon alternating dollops of vanilla and chocolate batter into the prepared loaf pan.
  9. Use a toothpick or skewer to gently swirl the batters together, creating a marble effect. Do not over-swirl.
  10. Bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs attached.
  11. Let the cake cool in the pan for 10 minutes before inverting it onto a wire rack to cool completely.