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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. Tender zucchini cake is layered with a light swirl so the streusel stays crisp while the crumb stays soft.
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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: 360
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
  • 0.333 cup brown sugar
  • 1.5 tsp cinnamon
  • 3 tbsp cold butter, cubed

Equipment

  • 1 sheet pan

Method
 

Prep
  1. Preheat the oven to 350°F and grease a 9x9 baking pan to prevent sticking.
  2. Make the cinnamon streusel by mixing flour, brown sugar, and cinnamon, then cut in the cold butter until crumbly with a sandy texture.
  3. Refrigerate the streusel until ready to use so the crumbs stay thick and hold their shape.
Mix the cake
  1. Whisk the cake flour, baking powder, baking soda, salt, and cinnamon until evenly combined.
  2. Beat granulated sugar, eggs, vegetable oil, sour cream, and vanilla extract until smooth.
  3. Stir in the grated squeezed zucchini so the batter looks evenly speckled.
  4. Fold the dry ingredients into the wet ingredients until just combined, stopping as soon as you no longer see dry flour.
Assemble and bake
  1. Pour the batter into the greased 9x9 pan and sprinkle half the streusel over the top.
  2. Add a light swirl through the batter and streusel so the layers show when sliced.
  3. Top with the remaining streusel to fully cover the surface for a thick crumb finish.
  4. Bake at 350°F for 35–42 minutes until a toothpick inserted in the center comes out clean.
  5. Cool for 15 minutes before cutting so the crumb sets and the streusel stays crisp on top.

Notes

For the best tender crumb and sliceable layers, squeeze the grated zucchini firmly and don’t overmix after adding the dry ingredients—stop when the flour disappears. Store covered in the fridge up to 3 days; rewarm individual slices briefly in a 300°F oven. Freezing is yes: freeze slices wrapped tightly for up to 2 months and thaw overnight in the fridge. If you want a slightly lighter option, swap sour cream for plain Greek yogurt 1:1.