Tool

• 8″ square baking pan

• Mixing bowls

• Electric hand mixer or stand mixer

Ingredients

Cinnamon filling

• ⅔ cup packed light brown sugar

• ¼ cup all‑purpose flour

• 2 teaspoons ground cinnamon

Streusel topping

• ¾ cup all‑purpose flour

• ½ cup packed light brown sugar

• 2 teaspoons ground cinnamon

• ¼ teaspoon salt

• 6 tablespoons cold unsalted butter, diced

Cake

• 1¾ cups all‑purpose flour

• 2 teaspoons baking powder

• ¾ teaspoon salt

• 10 tablespoons unsalted butter, softened

• ¾ cup granulated sugar

• ¼ cup packed light brown sugar

• 2 large eggs, room temperature

• ⅔ cup sour cream, room temperature

• 2 teaspoons vanilla extract

Vanilla glaze (optional)

• 1 cup powdered sugar

• 2 tablespoons whole milk

• ½ teaspoon vanilla extract

Direction

Make the cinnamon filling

• Whisk brown sugar, flour, and cinnamon together; set aside.

Make the streusel topping

• Whisk flour, brown sugar, cinnamon, and salt.

• Add cold diced butter; crumble with fingers or fork until mixture resembles wet sand.

• For larger crumbs, squeeze mixture together and break apart. Set aside.

Make the cake

• Preheat oven to 350°F. Grease an 8×8″ pan and line with parchment.

• Whisk flour, baking powder, and salt; set aside.

• Beat butter and both sugars on medium until light and fluffy (about 3 minutes).

• Add eggs one at a time, beating well after each.

• Add sour cream and vanilla; mix on low until combined.

• Add dry mixture; mix on low just until combined.

• Spread half the batter into the pan.

• Sprinkle cinnamon filling evenly over the batter.

• Dollop remaining batter on top; spread gently from center outward.

• Sprinkle streusel over the top, starting at edges and moving inward.

• Bake 55 minutes or until a toothpick comes out clean.

• Cool at least 30 minutes before serving.

Make the glaze (optional)

• Whisk powdered sugar, milk, and vanilla until smooth.

• Drizzle over cake before or after slicing.

Notes

• Store leftovers in an airtight container at room temperature for 3 days.

• Bake in a 9″ round pan with no changes.

• For a 9×13″ pan, double the recipe and bake about 1 hour; serve from the pan.

Nutrition

Calories: 623kcal Carbohydrates: 95g Protein: 6g Fat: 25g Saturated Fat: 15g Polyunsaturated Fat: 1g Monounsaturated Fat: 6g Trans Fat: 1g Cholesterol: 105mg Sodium: 389mg Potassium: 141mg Fiber: 2g Sugar: 64g Vitamin A: 796IU Vitamin C: 0.2mg Calcium: 130mg Iron: 2mg