Ingredients:

  • 1 ½ cups (180g) All-Purpose Flour (for streusel)
  • ¾ cup (150g) Light Brown Sugar, packed (for streusel)
  • ¼ cup (50g) Granulated Sugar (for streusel)
  • 1 teaspoon Ground Cinnamon (for streusel)
  • ½ cup (113g) Unsalted Butter, cold & cubed (for streusel)
  • ½ cup (100g) Light Brown Sugar, packed (for swirl)
  • 1 ½ teaspoons Ground Cinnamon (for swirl)
  • 2 tablespoons (30ml) Unsalted Butter, melted (for swirl)
  • 2 ½ cups (300g) All-Purpose Flour (for batter)
  • 1 cup (200g) Granulated Sugar (for batter)
  • 2 teaspoons Baking Powder (for batter)
  • ½ teaspoon Salt (for batter)
  • ½ cup (113g) Unsalted Butter, softened (room temperature)
  • 2 Large Eggs (room temperature)
  • 1 cup Full-fat Sour Cream or Plain Greek Yogurt
  • 1 teaspoon Vanilla Extract

Instructions:

  1. Preparation: Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch rectangular baking pan.
  2. Make the Streusel: In a medium bowl, combine the streusel dry ingredients (flour, brown sugar, granulated sugar, and cinnamon). Cut in the cold, cubed butter using your fingers or a pastry blender until the mixture resembles coarse crumbs. Set aside in the refrigerator to keep cold.
  3. Prepare the Swirl: In a small bowl, whisk together the swirl ingredients: brown sugar, cinnamon, and melted butter until fully incorporated and sandy. Set aside.
  4. Mix Dry Ingredients (Cake): Whisk together the cake batter dry ingredients (flour, sugar, baking powder, and salt) in a large bowl.
  5. Mix Wet Ingredients (Cake): In a separate bowl, briefly whisk the softened butter, eggs, sour cream, and vanilla extract until just combined.
  6. Combine Batter: Gradually add the wet ingredients to the dry ingredients. Mix on low speed until just combined; do not overmix. A few streaks of flour are acceptable.
  7. Layer the Cake: Scrape half of the cake batter into the prepared pan, spreading evenly. Gently dollop the cinnamon swirl mixture randomly over this batter layer.
  8. Swirl and Top: Use a knife or skewer to gently cut through the batter 2-3 times to create ribbons—do not over-swirl. Carefully spread the remaining cake batter over the top layer.
  9. Apply Topping: Retrieve the streusel from the fridge and sprinkle evenly and generously over the top of the cake batter.
  10. Bake: Bake for 40–45 minutes. The cake is done when a toothpick inserted into the center (avoiding the thick swirl areas) comes out with moist crumbs attached.
  11. Cool & Serve: Cool the cake in the pan on a wire rack for at least 20 minutes before slicing and serving warm or at room temperature.