Buttermilk-Soft Fluffy Vanilla Sheet Cake
Tall and buttermilk-soft, this fluffy vanilla sheet cake springs back when you press it - the one I carry to bake sales and birthdays. A full tablespoon of real vanilla puts the flavor right up front, and it stays moist for days.
Equipment
- 9x13 Metal Baking Pan
- Stand mixer or hand mixer
- Mixing Bowls
- Whisk and Spatula
- Parchment Paper
- Wire cooling rack
Ingredients
For the Cake
- 2 1/2 cups all-purpose flour, spooned and leveled
- 1 3/4 cups granulated sugar
- 3/4 cup unsalted butter, softened
- 3 large eggs, room temperature
- 1 cup buttermilk, room temperature
- 1/4 cup sour cream, room temperature
- 1 tablespoon vanilla extract
- 1 1/2 teaspoons baking powder
- 1/2 teaspoon baking soda
- 1 teaspoon salt
For the Vanilla Buttercream
- 1 cup unsalted butter, softened
- 4 cups powdered sugar, sifted if lumpy
- 2 tablespoons heavy cream, plus an extra splash if needed
- 2 teaspoons vanilla extract
- 1/4 teaspoon salt
Instructions
- Preheat the oven to 350°F with the rack in the center. Grease a 9x13 metal pan with butter or cooking spray, then line the bottom with parchment paper. Grease the parchment too, so the cake releases without a fight.
- Whisk the flour, baking powder, baking soda, and salt together in a medium bowl until evenly combined. Set aside.
- Beat the softened butter and sugar on medium-high speed for a full 3 to 4 minutes, scraping the bowl down halfway. Stop when the mixture looks pale, glossy, and noticeably lighter - soft whipped butter texture. This is the most important step for fluff. Do not rush it.
- Add the eggs one at a time, beating each until fully combined before adding the next. Add the vanilla and mix it in. If the mixture looks slightly curdled, do not panic; it comes back together once the flour goes in.
- With the mixer on low, add one-third of the flour mixture, then half of the buttermilk and sour cream (stir the sour cream into the buttermilk first), then another third of flour, the rest of the buttermilk, then the final third of flour. Mix just until the last streaks of flour disappear - about 20 to 30 seconds. Overmixing develops gluten and makes the cake tough.
- Scrape the batter into the prepared pan and smooth the top with a spatula. Tap the pan gently on the counter to pop any big air bubbles.
- Bake for 30 to 35 minutes, until the edges are deep honey-gold and pulling slightly away from the pan. Around 20 minutes the kitchen will smell like warm vanilla and toasted butter - that smell is information. At 30 minutes, press the center gently with two fingers. It should spring back completely; if it leaves a slow impression, give it five more minutes.
- A toothpick inserted into the center should come out clean or with a couple of moist crumbs, not wet batter. Let the cake cool in the pan on a wire rack for 15 minutes, then run a knife around the edges and turn it out onto the rack. Frost only after it is completely cool; a warm cake will melt the frosting.
- For the buttercream, beat the softened butter until creamy, then add the powdered sugar one cup at a time, alternating with the heavy cream and vanilla. Beat on medium-high for 2 to 3 minutes until light and fluffy. Add an extra splash of cream if it is too thick. Frost the cooled cake and cut into squares.
Notes
Room temperature matters here - set the butter, eggs, buttermilk, and sour cream out about an hour ahead so the creamed mixture stays smooth. A metal 9x13 pan bakes more evenly than glass; if you use glass, drop the oven to 325°F and expect a slightly longer bake. Store frosted or unfrosted cake covered at room temperature for 3 to 4 days, or freeze the unfrosted cake tightly wrapped for up to 3 months. For dairy-free, use plant-based stick butter, make buttermilk with oat milk and a splash of vinegar, and swap the sour cream for coconut cream. For gluten-free, use a 1:1 all-purpose flour blend and add two extra tablespoons of milk to the batter.