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"A beautifully frosted vanilla sheet cake in a rectangular dish with one square slice served on a plate."

Easy Vanilla Sheet Cake (Moist, Fluffy, Feeds a Crowd)

A moist, fluffy vanilla sheet cake made with sour cream and buttermilk for a tender crumb that stays soft for days. Baked and frosted in one 9x13-inch pan with silky vanilla buttercream. No stacking, no leveling, no stress.
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Prep Time 15 minutes
Cook Time 33 minutes
Chill Time 1 hour
Total Time 1 hour 48 minutes
Servings: 20 Servings
Course: Dessert
Cuisine: American
Calories: 420
Ingredients Equipment Method Notes

Ingredients
  

For the Sheet Cake
  • 2 1/2 cups all-purpose flour
  • 2 tbsp cornstarch do not skip
  • 2 1/2 tsp baking powder
  • 1/2 tsp baking soda
  • 1/2 tsp salt
  • 3/4 cup unsalted butter room temperature
  • 1 3/4 cups granulated sugar
  • 3 large eggs room temperature
  • 2 tsp vanilla extract
  • 1/2 cup sour cream room temperature
  • 3/4 cup buttermilk room temperature
For the Vanilla Buttercream
  • 1 1/2 cups unsalted butter softened
  • 5 cups powdered sugar sifted
  • 3-4 tbsp heavy cream
  • 2 tsp vanilla extract
  • 1 pinch salt

Equipment

  • 1 9x13-inch metal baking pan Nordic Ware recommended for even baking
  • 1 KitchenAid stand mixer or hand mixer
  • 1 Digital kitchen scale for precise flour measurement
  • 1 Offset spatula for frosting in the pan
  • Parchment paper for easy removal if desired
  • 1 Bench scraper optional, for smooth frosting finish

Method
 

  1. Preheat oven to 350 degrees F. Grease a 9x13-inch pan and line with parchment if desired.
    "A rectangular 9x13-inch metal baking pan lined with parchment paper sitting on a light oak wooden counter, with an oven preheating to 350 degrees Fahrenheit in the background."
  2. Whisk flour, cornstarch, baking powder, baking soda, and salt in a bowl. Set aside.
    "A large glass bowl filled with whisked all-purpose flour, cornstarch, baking powder, baking soda, and salt on a bright wooden kitchen counter."
  3. Beat butter on medium-high for 2 minutes. Add sugar and beat 3 to 4 minutes until pale and fluffy.
    "A large glass bowl containing creamed butter and sugar, beaten until pale, light, and fluffy, sitting on a wooden kitchen counter."
  4. Add eggs one at a time on medium speed. Add vanilla. Mix until combined.
    "A large glass bowl containing creamed butter and sugar mixture with a fresh splash of dark liquid vanilla extract, ready to be mixed on a light oak kitchen surface."
  5. Add sour cream on low. Mix until just combined (batter may look slightly curdled — this is fine).
    "A large glass bowl on a stand mixer containing cake batter mixed with sour cream, shown on a light oak kitchen surface."
  6. Add flour mixture in three additions, alternating with buttermilk in two additions. Mix on low, stopping as soon as each addition is incorporated.
    "A large glass bowl with creamy vanilla cake batter, showing the final stage of mixing flour and buttermilk, on a wooden kitchen counter."
  7. Pour batter into pan. Spread evenly to edges. Bake 28 to 33 minutes until toothpick comes out clean.
    "Vanilla sheet cake batter poured and spread evenly into a 9x13-inch rectangular metal pan, ready to be placed in the oven."
  8. Cool completely in pan, at least 1 hour, before frosting.
    "A freshly baked, golden-brown rectangular vanilla sheet cake in a metal pan, cooling on a wire rack on a wooden kitchen counter."
  9. For buttercream: beat butter 3 minutes until pale. Add powdered sugar cup by cup on low. Add cream by the tablespoon. Add vanilla and salt. Beat on medium 2 minutes until smooth.
    "A glass mixing bowl filled with smooth, creamy, and pale white vanilla buttercream frosting on a wooden kitchen counter."
  10. Spread buttercream directly onto cooled cake in the pan. Slice and serve.
    "A freshly baked vanilla sheet cake in a metal pan, topped with a generous layer of smooth, creamy vanilla buttercream, sitting next to a kitchen knife."

Notes

  • Do not skip the cornstarch. It creates a noticeably softer, more tender crumb.
  • The 3 to 4 minute creaming step builds the air that creates a light, open crumb. Do not rush it.
  • Cool completely before frosting or the buttercream will melt.
  • Start checking the cake at 26 minutes. Sheet cakes overbake faster than layer cakes.
  • Store covered at room temperature for up to 3 days, refrigerated for up to 5 days.