Ingredients:

  • 2 cups All-Purpose Flour (spooned and levelled)
  • 2 teaspoons Baking Powder
  • 1/2 teaspoon Baking Soda
  • 1/2 teaspoon Fine Sea Salt
  • 1/2 teaspoon Ground Cinnamon (for batter)
  • 1/2 cup Unsalted Butter, softened (1 stick)
  • 3/4 cup Granulated Sugar
  • 2 Large Eggs, room temperature
  • 1 teaspoon Vanilla Extract
  • 3/4 cup Buttermilk, room temperature
  • 1/2 cup Light Brown Sugar, packed (for swirl)
  • 1 tablespoon Ground Cinnamon (for swirl)
  • 1 teaspoon All-Purpose Flour (for swirl)
  • 1 tablespoon Melted Unsalted Butter (for swirl)
  • 1/2 cup Powdered Sugar (optional, for glaze)
  • 2-3 tablespoons Milk or Cream (optional, for glaze)
  • 1/4 teaspoon Vanilla Extract (optional, for glaze)

Instructions:

  1. Preheat your oven to 350°F (175°C). Grease and line a 9x5 inch loaf pan with parchment paper, leaving an overhang 'sling'.
  2. Combine Dry Ingredients: In a large bowl, whisk together the 2 cups flour, baking powder, baking soda, salt, and 1/2 teaspoon cinnamon. Set aside.
  3. Prepare Filling: In a small bowl, combine the brown sugar, 1 tablespoon cinnamon, 1 teaspoon flour, and the melted butter until the mixture resembles wet sand. Set aside.
  4. Cream Butter and Sugar: Using an electric mixer, beat the softened butter and granulated sugar together on medium speed until the mixture is pale yellow and fluffy (3-5 minutes).
  5. Add Wet Ingredients: Beat in the eggs, one at a time, ensuring each is fully incorporated. Scrape down the sides of the bowl. Mix in the vanilla extract.
  6. Finish Batter: Reduce mixer speed to low. Add half of the dry mixture, mixing only until just combined. Pour in all of the buttermilk, mixing briefly. Add the remaining dry ingredients and mix until no pockets of flour remain. Do not overmix.
  7. Layer Batter and Swirl: Spoon about half of the batter into the prepared loaf pan. Sprinkle 2/3 of the cinnamon swirl filling evenly over the batter. Gently dollop the remaining batter over the filling layer, smoothing slightly to cover. Sprinkle the remaining 1/3 filling over the very top of the loaf.
  8. Swirling: Use a long wooden skewer or butter knife to gently cut through the batter in an 'S' motion two or three times to create the marble effect.
  9. Bake: Place the loaf in the preheated oven and bake for 55–65 minutes. Check doneness by inserting a skewer into the center; it should come out clean.
  10. Cool and Glaze: Let the loaf cool in the pan for 10–15 minutes before using the parchment sling to transfer it to a wire rack. Cool completely. If glazing, whisk together powdered sugar, milk/cream, and vanilla until smooth, then drizzle over the cooled loaf before serving.