Ingredients

1. The Cinnamon Ribbon & Streusel Topping

(Note: This serves as both the middle layer and the crumbly top)

  • 1 cup light brown sugar, packed

  • ½ cup all-purpose flour

  • 2 ½ teaspoons ground cinnamon

  • ⅓ cup unsalted butter, melted

2. The Cake Base

  • 2 cups all-purpose flour

  • 1 teaspoon baking powder

  • ½ teaspoon baking soda

  • ½ teaspoon salt

  • ½ cup unsalted butter, softened to room temperature

  • ¾ cup granulated white sugar

  • 2 large eggs, room temperature

  • 1 teaspoon pure vanilla extract

  • 1 cup sour cream (or plain Greek yogurt), room temperature

3. The Vanilla Glaze

  • ½ cup powdered sugar

  • 1 tablespoon milk (or heavy cream)

  • ¼ teaspoon vanilla extract

Instructions

Step 1: Prep Work

  1. Preheat your oven to 350°F (175°C).

  2. Grease an 8×8-inch or 9×9-inch square baking pan with butter or non-stick spray, or line it with parchment paper for easy removal.

Step 2: Make the Streusel & Ribbon

  1. In a medium bowl, mix the brown sugar, flour, and cinnamon together.

  2. Pour in the melted butter and stir with a fork until the mixture forms coarse, wet crumbs. Set this aside.

Step 3: Mix the Cake Batter

  1. Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

  2. Wet Ingredients: In a large bowl (or stand mixer), beat the softened butter and granulated sugar together on medium-high speed for about 2 minutes until light and fluffy.

  3. Add the eggs one at a time, beating well after each. Stir in the vanilla extract.

  4. Combine: Alternate adding the dry ingredients and the sour cream to the wet mixture (start with 1/3 dry, half the sour cream, 1/3 dry, the rest of the sour cream, and the final dry ingredients). Mix on low speed just until combined. Do not overmix.

Step 4: Assemble the Cake

  1. Spread half of the cake batter evenly into the bottom of your prepared baking pan.

  2. Sprinkle half of your prepared cinnamon streusel mixture evenly over the batter to create the middle ribbon layer.

  3. Carefully dollop the remaining cake batter over the cinnamon layer and smooth it out gently with a spatula.

  4. Sprinkle the remaining streusel mixture evenly over the top of the cake.

Step 5: Bake

  1. Bake for 35 to 40 minutes. The cake is done when a toothpick inserted into the center comes out clean or with just a few moist crumbs.

  2. Place the pan on a wire rack and let the cake cool for at least 20 minutes before glazing.

Step 6: Glaze and Serve

  1. In a small bowl, whisk the powdered sugar, milk, and vanilla extract together until smooth. If it’s too thick, add a few more drops of milk; if too thin, add a pinch more powdered sugar.

  2. Use a spoon or fork to drizzle the glaze across the top of the cooled cake.

  3. Slice into squares and enjoy!