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Cinnamon Sugar Zucchini Coffee Cake

Cinnamon sugar zucchini coffee cake with a thick, crumbly cinnamon brown sugar streusel covering the entire top. This easy coffee cake bakes up tender with visible layers when sliced and a light swirl in the center.
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Prep Time 20 minutes
Cook Time 40 minutes
cooling 15 minutes
Total Time 1 hour 15 minutes
Servings: 12 servings
Course: Breakfast
Cuisine: American
Calories: 310
Ingredients Equipment Method Notes

Ingredients
  

Cake
  • 1.5 cup all-purpose flour
  • 1 tsp baking powder
  • 0.5 tsp baking soda
  • 0.5 tsp salt
  • 1 tsp cinnamon
  • 0.75 cup granulated sugar
  • 2 eggs
  • 0.33 cup vegetable oil
  • 0.5 cup sour cream
  • 1 tsp vanilla extract
  • 1 cup zucchini grated and squeezed dry
Cinnamon Streusel
  • 0.5 cup all-purpose flour
  • 0.33 cup brown sugar
  • 1.5 tsp cinnamon
  • 3 tbsp cold butter cubed

Equipment

  • 1 sheet pan

Method
 

Prep & preheat
  1. Preheat the oven to 350°F and grease a 9x9 baking pan so the cake releases cleanly after baking.
  2. Let the streusel chill in the refrigerator while you mix the batter so the crumbs stay thick and crumbly.
Make cinnamon streusel
  1. Mix the flour, brown sugar, and cinnamon together for the streusel in a bowl until evenly combined.
  2. Cut in the cold butter with your fingertips or a fork until the mixture looks like coarse crumbs with no large butter chunks.
  3. Refrigerate the streusel so it firms up and creates a dense top layer.
Make the cake batter
  1. Whisk the all-purpose flour, baking powder, baking soda, salt, and cinnamon together until the dry ingredients are evenly speckled.
  2. Beat the granulated sugar, eggs, vegetable oil, sour cream, and vanilla extract until the mixture looks smooth and glossy.
  3. Stir in the grated, squeezed-dry zucchini so it’s evenly distributed through the batter.
  4. Fold the dry ingredients into the wet ingredients just until combined, stopping as soon as no dry streaks remain.
Assemble & bake
  1. Pour the batter into the prepared 9x9 pan and spread it into an even layer.
  2. Sprinkle half the streusel over the batter to anchor the crumb topping.
  3. Swirl lightly so you can see a ribbon of cake under the streusel when sliced.
  4. Top with the remaining streusel to cover the entire surface thickly.
  5. Bake for 35–42 minutes at 350°F until a toothpick in the center comes out clean.
  6. Cool for 15 minutes before cutting so the thick streusel sets and the tender crumb holds its layers.

Notes

Pro tip: squeeze the grated zucchini very well so the cake bakes up tender, not wet, and the streusel stays crisp. Store covered in the fridge up to 3 days; reheat briefly in the microwave for a softer crumb. Freezing is not recommended because the zucchini can release moisture after thawing. For a dairy-light swap, use plain low-fat yogurt in place of sour cream (same amount) for a similar tang.