A half sheet cake is a generous, rectangular cake baked in a rimmed pan and finished with a smooth layer of frosting. This version uses a tender vanilla buttermilk batter, bakes evenly in a standard 13-by-18-inch half sheet pan, and is easy to decorate and slice for a crowd.
Ingredients
- 3 cups (375 g) all-purpose flour, spooned into the measuring cups and leveled
- 2 cups (400 g) granulated sugar
- 2 teaspoons baking powder
- 1 teaspoon baking soda
- 1 teaspoon fine salt
- 1 cup (227 g) unsalted butter, softened
- 4 large eggs (about 200 g without shells), at room temperature
- 1 tablespoon (15 ml) vanilla extract
- 1¼ cups (300 ml) buttermilk, at room temperature
- For the frosting: 1 cup (227 g) unsalted butter, softened
- 4 cups (480 g) powdered sugar, sifted if lumpy
- 3 tablespoons (45 ml) milk, plus more as needed
- 1 teaspoon vanilla extract
- ¼ teaspoon fine salt
- Optional: ½ cup (about 85 g) sprinkles for decorating
Instructions
- Prepare the pan and oven. Set a rack in the middle of the oven and preheat to 350°F (175°C). Grease a 13-by-18-inch rimmed half sheet pan, line the bottom with parchment, and lightly grease the parchment. Use a rimmed pan at least 1 inch deep so the batter does not overflow; a smaller jelly-roll pan is not an equivalent substitute.
- Combine the dry ingredients. Whisk the flour, baking powder, baking soda, and salt together in a medium bowl. Set aside.
- Cream the butter and sugar. In a large bowl, beat the softened butter and granulated sugar with a hand mixer or stand mixer on medium speed for 2 to 3 minutes, until pale and fluffy. Scrape down the bowl. Beat in the eggs one at a time, mixing after each addition, then mix in the vanilla. If the mixture looks slightly curdled, continue; it will smooth out when the flour mixture is added.
- Finish the batter. Add about one-third of the flour mixture and mix on low just until partly combined. Add half the buttermilk, then another third of the flour, the remaining buttermilk, and the final flour. Mix only until no dry streaks remain, scraping the bowl as needed. Do not beat for a long time once the flour is in, which can make the cake dense.
- Fill and bake. Scrape the batter into the prepared pan and spread it evenly into the corners. Bake for 24 to 28 minutes, rotating the pan once after about 18 minutes if your oven browns unevenly. The cake is done when the top springs back lightly and a toothpick inserted near the center comes out clean or with a few moist crumbs. If using a food thermometer, the center should reach at least 200°F (93°C) for a set cake crumb; this is a quality check, not a USDA safety temperature requirement for cake.
- Cool completely. Let the cake cool in the pan on a rack for 20 minutes, then leave it in the pan until fully cool, about 45 minutes more. Frosting a warm cake will melt the butter and slide off. The cooling time is included in the total time.
- Make the frosting. Beat the softened butter on medium speed until creamy, about 2 minutes. Add the powdered sugar in two or three additions, mixing on low to avoid a cloud of sugar. Add the milk, vanilla, and salt; beat on medium for 1 to 2 minutes until smooth and spreadable. Add more milk 1 teaspoon (5 ml) at a time if it is too stiff, or a little more powdered sugar if it is too loose.
- Frost and cut. Spread the frosting over the completely cooled cake, reaching the edges. Add sprinkles while the frosting is still soft, if desired. Cut into 24 pieces with a long, clean knife, wiping it between cuts for neater squares.
Tips
- Measure flour lightly. Scooping straight from the bag can pack in too much flour. Spoon it into the cup and level it, or weigh the 375 g listed for a more consistent crumb.
- Bring ingredients to room temperature. Cool eggs and cold buttermilk can firm the butter and make the batter less even. Set them out for about 30 minutes before mixing; do not leave perishable ingredients at room temperature for more than 2 hours.
- Check your pan size. This recipe is written for a 13-by-18-inch pan. A deeper or smaller pan changes the bake time and can cause overflow; for a smaller pan, divide the batter rather than filling it beyond about two-thirds full.
- Use a sturdy base if transporting. Keep the cake in its pan or set it on a sheet cake board before frosting. Chill it briefly if the frosting needs to firm up for travel.
Serving Suggestions
Serve the cake at room temperature so the crumb is soft and the buttercream is easy to cut. It makes about 24 moderate party portions; cut it into 30 smaller squares for a dessert table or 18 larger servings. Pair it with fresh berries, sliced strawberries, or coffee. For clean edges, use a long knife and wipe away crumbs between cuts.
Variations
Chocolate sheet cake: Replace ½ cup (60 g) of the flour with ½ cup (40 g) unsweetened cocoa powder. The cake will be less vanilla-forward and slightly richer; sift the cocoa with the dry ingredients. A chocolate buttercream also works with this base.
Lemon cake: Add 2 tablespoons (12 g) finely grated lemon zest to the sugar and rub it in with your fingertips before creaming. Replace the vanilla in the frosting with 1 tablespoon (15 ml) lemon juice, adding it gradually so the frosting stays spreadable.
Different frosting: Use a simple cream cheese frosting if you prefer a tangier finish, but keep the frosted cake refrigerated. You can also tint the buttercream with a small amount of gel food coloring; liquid coloring may thin it.
Storage and Reheating
Because the cake contains butter and eggs, refrigerate leftovers within 2 hours. Store covered in the pan or in an airtight container for 3 to 4 days. For the best texture, let a portion sit at room temperature for 20 to 30 minutes before serving; cake does not need reheating. Freeze unfrosted cake, or individually wrapped frosted pieces, for up to 2 months. Thaw overnight in the refrigerator, then bring to room temperature before serving. Do not leave the cake out for extended periods, especially in a warm room.
Frequently Asked Questions
What size pan is a half sheet cake pan?
A common home half sheet pan measures about 13 by 18 inches, usually with a rim around 1 inch high. Commercial pan dimensions can vary slightly, so check the interior measurement and use a rimmed pan.
How many people does a half sheet cake serve?
This cake is cut into 24 party-size pieces. It can serve about 30 people if you make smaller dessert portions, or fewer if you cut larger pieces.
Can I make the cake a day ahead?
Yes. Bake it, cool it completely, cover the pan, and refrigerate it overnight, or bake and freeze the unfrosted cake. Frost it once fully thawed or chilled, then serve it at room temperature for a softer crumb.
Can I use regular milk instead of buttermilk?
Yes. Mix 1 tablespoon (15 ml) lemon juice or white vinegar into a measuring cup, add milk to reach 1¼ cups (300 ml), and let it stand for 5 to 10 minutes. This quick substitute is slightly less rich than buttermilk but provides the acidity the baking soda needs.
Why did my cake turn out dense?
Common causes include too much flour, overmixing after adding flour, or butter and eggs that were too cold to combine smoothly. Measure carefully, mix only until the batter is uniform, and check that the cake is fully baked before removing it.
Can I bake this in two smaller pans?
Yes, provided the pans have enough combined capacity and are not filled more than about two-thirds full. Baking time will likely be shorter, so start checking early with a toothpick and remove each pan when its center is set.
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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes
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