Ingredients:

  • ½ cups All-Purpose Flour (Streusel)
  • ¾ cup Light Brown Sugar, packed (Streusel)
  • ¼ cup Granulated Sugar (Streusel)
  • teaspoon Ground Cinnamon (Streusel)
  • stick (½ cup) Unsalted Butter, cold & cubed (Streusel)
  • ¾ cup Light Brown Sugar, packed (Swirl)
  • tablespoon Ground Cinnamon (Swirl)
  • tablespoons Unsalted Butter, softened (Swirl)
  • cups All-Purpose Flour (Cake)
  • ½ cups Granulated Sugar (Cake)
  • tablespoon Baking Powder (Cake)
  • ¾ teaspoon Salt (Cake)
  • cup (2 sticks) Unsalted Butter, softened (Cake)
  • large Eggs, room temperature
  • cup Sour Cream or Full-Fat Greek Yogurt, room temperature
  • ½ cup Milk (Whole or 2%), room temperature
  • teaspoons Vanilla Extract

Instructions:

  1. Preheat oven to 350°F (175°C). Grease and lightly flour a 9x13 inch baking pan, or line with parchment paper with an overhang.
  2. Make the Streusel: Whisk the streusel dry ingredients (flour, brown sugar, granulated sugar, cinnamon). Cut in the cold, cubed butter using a pastry blender or fingers until the mixture resembles coarse crumbs. Set aside in the refrigerator.
  3. Make the Cinnamon Swirl: Cream the softened butter for the swirl. Gradually beat in the brown sugar and cinnamon until a thick, spreadable paste forms. Set aside.
  4. Mix Dry Cake Ingredients: Whisk together the cake flour, granulated sugar, baking powder, and salt in a large bowl.
  5. Cream Butter & Eggs: Cream the softened cake butter until pale and fluffy. Add eggs one at a time, beating well after each addition. Beat in the vanilla extract.
  6. Combine Wet and Dry: Alternate adding the dry ingredients mixture with the sour cream and milk to the butter mixture, beginning and ending with the dry. Mix only until just combined—a few lumps are fine. Do not overmix.
  7. Layer the Cake: Pour half of the batter into the prepared pan and spread evenly. Drop spoonfuls of the cinnamon swirl mixture evenly over the batter layer. Gently swirl it through the batter using a knife in light figure-eight motions.
  8. Top Layers: Pour the remaining cake batter over the swirl layer, spreading gently to cover. Generously scatter the chilled streusel topping evenly over the top layer of batter.
  9. Bake for 45 to 55 minutes, or until a wooden skewer inserted into the center comes out clean (avoiding the swirl layer if possible).
  10. Let the coffee cake cool completely in the pan on a wire rack before slicing and serving.