Preheat your oven to 350 degrees F. Make sure your oven is heated before you start mixing the batter, as this helps the cake rise properly. While it’s heating up, prepare your baking pan by spraying a 9x13-inch baking pan with nonstick spray. This will ensure an easy release once the cake is baked.
Next, shred the zucchini using the largest holes of a box grater or the shredding attachment of a food processor. I always squeeze out the extra moisture with a kitchen towel or paper towel to avoid a soggy cake. Set the shredded zucchini aside while you mix the other ingredients.
In a large mixing bowl, whisk together the vegetable oil, Greek yogurt, eggs, and granulated white sugar until the mixture is smooth and well combined. This step is crucial for incorporating air into the batter.
In another bowl, whisk together the dry ingredients: all-purpose flour, baking powder, baking soda, ground cinnamon, and fine sea salt. Mixing these dry ingredients well ensures that your cake rises evenly.
Add the dry mixture to the wet mixture in two additions, stirring gently to combine after each addition. Before the batter is completely combined, fold in the shredded zucchini and blueberries. Be careful not to overmix; you want to see a few flecks of flour still visible.
Transfer the batter to the prepared baking pan. Spread it evenly, ensuring that the batter reaches the corners of the pan. This will help the cake bake evenly and avoid any undercooked spots.
Bake for 30 to 35 minutes, or until a toothpick inserted into the center of the cake comes out clean. Keep an eye on it towards the end of the baking time, as ovens can vary.
Once removed from the oven, allow the cake to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely. It’s important to let the cake cool completely before frosting to avoid melting the frosting.
For the frosting, use a hand mixer to combine the cream cheese and unsalted butter in a bowl. Mix until creamy and smooth. Gradually add the vanilla, fine sea salt, and powdered sugar. Mix on low speed until the frosting is smooth, scraping down the sides of the bowl as needed.
Once the cake is completely cool, spread the frosting evenly on top. Cut into squares, serve, and enjoy your delicious Blueberry Zucchini Sheet Cake!