Ingredients:

  • 1 cup All-Purpose Flour (Streusel)
  • 1/2 cup Light Brown Sugar, packed (Streusel)
  • 1/4 cup Granulated Sugar (Streusel)
  • 1 teaspoon Ground Cinnamon (Streusel)
  • 1/4 teaspoon Ground Nutmeg (Streusel)
  • 6 tablespoons Unsalted Butter, cold & cubed (Streusel)
  • 1/2 cup Light Brown Sugar, packed (Swirl)
  • 1 tablespoon All-Purpose Flour (Swirl)
  • 1 teaspoon Ground Cinnamon (Swirl)
  • 1/2 teaspoon Ground Ginger (Swirl)
  • 2 1/4 cups All-Purpose Flour (Cake Batter)
  • 2 teaspoons Baking Powder (Cake Batter)
  • 1/2 teaspoon Baking Soda (Cake Batter)
  • 1/2 teaspoon Salt (Cake Batter)
  • 1/2 cup Unsalted Butter, softened (Cake Batter)
  • 1 cup Granulated Sugar (Cake Batter)
  • 2 Large Eggs (Cake Batter)
  • 1 cup Pure Pumpkin Purée (Cake Batter)
  • 1 teaspoon Vanilla Extract (Cake Batter)
  • 1/2 cup Sour Cream or Plain Full-Fat Yogurt (Cake Batter)

Instructions:

  1. Preheat oven to 350°F (175°C). Grease and flour the 9x13 inch pan, then line the bottom with parchment paper, leaving an overhang for easy removal.
  2. Make the Streusel: Whisk dry streusel ingredients (flour, brown sugar, granulated sugar, cinnamon, nutmeg) together in a medium bowl. Cut in the cold, cubed butter using a pastry blender or fingertips until coarse, pea-sized crumbs form. Set aside in the fridge to keep cold.
  3. Mix the Swirl: In a small bowl, thoroughly combine all swirl ingredients (brown sugar, flour, spices). Set aside.
  4. Combine Dry Cake Ingredients: Whisk together the flour, baking powder, baking soda, and salt in a separate bowl. Set aside.
  5. Cream Butter and Sugar: In a large bowl, beat the softened butter and granulated sugar until light and fluffy (about 3 minutes with a mixer).
  6. Incorporate Wet Ingredients: Beat in eggs one at a time, scraping down the sides. Mix in the pumpkin purée and vanilla extract until just combined.
  7. Alternate Dry and Wet: Gradually add the dry ingredient mixture to the wet ingredients, alternating with the sour cream (begin and end with dry). Mix only until just combined. Do not overmix.
  8. Assemble the Layers: Spoon half of the cake batter into the prepared pan and spread evenly.
  9. Add Swirl and Topping: Sprinkle the entire pumpkin swirl mixture evenly over the first layer of batter. Then, sprinkle the reserved, chilled streusel topping evenly over the swirl layer.
  10. Final Layer: Carefully spoon the remaining cake batter over the streusel/swirl mixture. Spread gently with a spatula to cover, trying not to disturb the layers underneath too much.
  11. Bake for 50–60 minutes, or until a wooden skewer inserted near the centre comes out clean.
  12. Allow the cake to cool completely in the pan on a wire rack before slicing.