Ingredients:

  • 2 ½ cups (315g) All-Purpose (Plain) Flour
  • 2 teaspoons Baking Powder
  • ½ teaspoon Fine Sea Salt
  • 1 ½ cups (300g) Granulated Sugar
  • ½ cup (113g or 1 stick) Unsalted Butter, softened (for cake)
  • ¼ cup (60ml) Neutral Oil (e.g., canola or vegetable)
  • 3 large Eggs, room temperature
  • 1 teaspoon Pure Vanilla Extract
  • 1 cup (240g) Full-Fat Sour Cream, room temperature
  • 1 cup (200g) Light Brown Sugar, firmly packed (for filling)
  • 2 teaspoons Ground Cinnamon (for filling)
  • ½ cup (113g or 1 stick) Unsalted Butter, melted (for filling)
  • 2 cups (240g) Icing Sugar (Powdered Sugar), sifted (for glaze)
  • ¼ cup (60ml) Milk or Heavy Cream (for glaze)
  • 1 teaspoon Pure Vanilla Extract (for glaze)
  • Pinch of Fine Sea Salt (for glaze)

Instructions:

  1. Preheat oven to 350°F (175°C). Grease and lightly flour the 9x13-inch baking pan.
  2. Combine Dry Ingredients: Whisk together the flour, baking powder, and salt in a medium bowl. Set aside.
  3. Cream Fats and Sugar: Using an electric mixer, cream the softened butter, granulated sugar, and oil on medium speed until pale and fluffy (about 3–4 minutes). Scrape down the bowl.
  4. Add Eggs and Vanilla: Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
  5. Alternate Wet/Dry: Reduce speed to low. Add half of the flour mixture, mixing until just combined. Add the sour cream and mix gently. Finish by adding the remaining flour mixture, mixing only until no streaks of flour remain. Do not overmix.
  6. Make the Filling: In a small bowl, whisk together the melted butter, brown sugar, and cinnamon until a thick, gooey paste forms.
  7. Layer the Cake: Spread half of the cake batter evenly into the prepared baking pan.
  8. Add the Filling: Carefully spoon the entire cinnamon filling mixture over the batter layer. Spread it gently to cover the surface, leaving a small border.
  9. Top Layer and Swirl: Gently dollop the remaining cake batter over the filling layer. Use an offset spatula to carefully spread the final batter layer. Insert a butter knife about half an inch deep and gently swirl it 4–5 times across the pan for a subtle swirl.
  10. Bake: Bake for 45–50 minutes, or until a wooden skewer inserted into the centre comes out clean or with moist crumbs attached.
  11. Cool: Transfer the cake to a cooling rack and let it cool for 15 minutes.
  12. Prepare the Glaze: While the cake is cooling, whisk together the sifted icing sugar, milk/cream, vanilla, and salt until smooth and pourable.
  13. Glaze the Cake: While the cake is still slightly warm, pour the glaze evenly over the top. Allow the glaze to set fully (about 10–15 minutes) before slicing and serving.