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Lightened-Up Birthday Sheet Cake with Rainbow Sprinkle Buttercream

lightened-up birthday sheet cake - featured image
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A tender, moist sheet cake with a fluffy, less-sweet buttercream that delivers pure birthday joy without the sugar hangover. This one-bowl wonder uses Greek yogurt and cream cheese to lighten things up while keeping every bite deliciously nostalgic.

Ingredients

Scale
  • 1 ½ cups (190g) all-purpose flour
  • 1 cup (200g) granulated sugar
  • ½ cup (120g) plain Greek yogurt (full-fat or 2%)
  • ¼ cup (60ml) vegetable oil
  • 2 large eggs, at room temperature
  • ½ cup (120ml) milk (any kind)
  • 2 teaspoons vanilla extract
  • 1 ½ teaspoons baking powder
  • ¼ teaspoon baking soda
  • ½ teaspoon salt
  • ½ cup (113g) unsalted butter, softened
  • 4 ounces (113g) cream cheese, softened
  • 3 cups (360g) powdered sugar
  • 1 teaspoon vanilla extract
  • 1–2 tablespoons milk
  • ⅓ cup rainbow sprinkles (jimmies)

Instructions

  1. Preheat your oven to 350°F (175°C). Line your 9×13-inch pan with parchment paper, leaving a little overhang on the long sides. Lightly grease the parchment and the exposed sides of the pan with a little oil or cooking spray.
  2. In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt. Make sure there are no lumps.
  3. In a separate medium bowl or a large liquid measuring cup, whisk together the Greek yogurt, oil, eggs, milk, and vanilla extract. Whisk until the mixture is smooth and the yogurt is fully incorporated.
  4. Pour the wet ingredients into the bowl with the dry ingredients. Using a rubber spatula or a wooden spoon, gently fold the mixture together. Stir just until you no longer see streaks of flour. A few small lumps are perfectly fine. Do not over-mix.
  5. Pour the batter into the prepared pan and spread it into an even layer. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs attached. The top should be golden brown and spring back lightly when touched.
  6. Place the pan on a wire rack and let the cake cool in the pan for about 15 minutes. Then, using the parchment overhang, lift the cake out of the pan and transfer it to the wire rack to cool completely. This is critical—the cake must be completely cool before frosting.
  7. While the cake is cooling, make the frosting. In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer and a large bowl), beat the softened butter and cream cheese together on medium speed until smooth, light, and fluffy, about 2-3 minutes. Scrape down the sides and bottom of the bowl.
  8. With the mixer on low speed, gradually add the powdered sugar, about ½ cup at a time. Mix until each addition is incorporated before adding the next. Add the vanilla extract and 1 tablespoon of milk. Increase the speed to medium-high and beat for 2-3 minutes, until the frosting is light and fluffy. If it’s too thick, add the remaining tablespoon of milk. If it’s too thin, add a little more powdered sugar.
  9. Using a rubber spatula, gently fold in the rainbow sprinkles. Be careful not to over-mix, or the color from the sprinkles will bleed and turn your frosting a muddy grey. Fold just until they are evenly distributed.
  10. Once the cake is completely cool, place it on a serving platter or cutting board. Using an offset spatula, spread the buttercream evenly over the top of the cake. Add a few extra sprinkles on top for a festive finish.
  11. For clean slices, use a sharp knife and wipe it clean between each cut. This cake is delicious at room temperature or slightly chilled.

Notes

Don’t over-mix the batter—a few lumps are fine. Room temperature ingredients are essential for proper emulsification. Let the cake cool completely before frosting to avoid a melty mess. For the buttercream, use jimmies-style sprinkles to minimize color bleeding. The cake can be made a day ahead and frosted the next day.

Nutrition

Keywords: lightened-up birthday cake, sheet cake, rainbow sprinkle buttercream, healthy birthday cake, Greek yogurt cake, easy sheet cake, one-bowl cake

Find it online: https://ovenmila.com/lightened-up-birthday-sheet-cake-with-rainbow-sprinkle-buttercream/