Ingredients:

  • 1 cup All-Purpose Flour (for streusel)
  • ½ cup Unsalted Butter, chilled and cubed (for streusel)
  • ½ cup Light Brown Sugar, packed (for streusel)
  • ¼ cup Granulated Sugar (for streusel)
  • 2 tsp Ground Cinnamon
  • ½ tsp Fine Sea Salt (for streusel)
  • 2 cups All-Purpose Flour (for batter)
  • 1 tsp Baking Soda
  • 1 tsp Baking Powder
  • ½ tsp Fine Sea Salt (for batter)
  • 1 cup Unsalted Butter, softened to room temperature (for batter)
  • 1 cup Granulated Sugar (for batter)
  • 2 large Eggs, room temperature
  • 1 Tbsp Pure Vanilla Extract
  • 1 cup Full-Fat Sour Cream, room temperature
  • ½ cup Confectioners' Sugar (for glaze, optional)
  • 2 Tbsp Milk or Lemon Juice (for glaze, optional)

Instructions:

  1. Preheat your oven to 350°F (175°C). Grease and flour a 9-inch baking pan, or line the bottom with parchment paper.
  2. Prepare the Streusel: In a medium bowl, whisk together the streusel flour, sugars, cinnamon, and salt. Cut the chilled, cubed butter into the dry ingredients until the mixture resembles coarse crumbs. Set aside.
  3. Whisk the Cake Dry Ingredients: In a separate medium bowl, whisk together the batter flour, baking soda, baking powder, and salt.
  4. Cream Butter and Sugar: In the bowl of a stand mixer, beat the softened butter and granulated sugar on medium speed until light and fluffy (3–5 minutes).
  5. Add Wet Ingredients: Beat in the eggs one at a time, ensuring each is fully incorporated. Stir in the vanilla extract. Scrape down the sides of the bowl.
  6. Alternate Dry and Wet: Reduce the mixer speed to low. Gradually add the flour mixture in three additions, alternating with the sour cream in two additions (beginning and ending with the flour). Mix only until just combined; do not overmix.
  7. Layer the Batter: Spoon half of the cake batter into the prepared pan and spread it gently and evenly.
  8. Add Streusel Layer: Sprinkle about two-thirds of the prepared streusel mixture evenly over the top of the batter.
  9. Finish Layering: Carefully spoon the remaining cake batter over the streusel layer, smoothing the top. Sprinkle the remaining streusel mixture over the top.
  10. Bake: Bake for 45–50 minutes, or until a wooden skewer inserted into the centre comes out clean. If the top browns too quickly, tent lightly with aluminum foil.
  11. Cool: Let the cake cool in the pan on a wire rack for 15 minutes before releasing it and allowing it to cool completely.
  12. Glaze (Optional): Whisk the confectioners' sugar and milk (or lemon juice) together until smooth. Drizzle the glaze decoratively over the cooled cake before serving.