This simple one layer chocolate cake is baked in a 9×13-inch pan and finished with a rich chocolate sour cream frosting. The cake stays super moist and tender thanks to buttermilk and neutral oil. No special equipment or advanced decorating skills required — perfect for birthdays, potlucks, bake sales, or any gathering where you need to serve a crowd.
I often adapt my trusted chocolate cake formulas into sheet cakes when readers ask for an easier format. Using a tried-and-true chocolate batter in a 9×13-inch pan produced a reliable, moist chocolate buttermilk sheet cake that’s easy to slice and serve. It’s ideal when you want something that both looks and tastes great without fuss.
If you prefer vanilla, the same approach works for a vanilla sheet cake — and you can use many frosting options. A sheet cake is forgiving: no piping bags or cake turntables required. Spread the frosting, add sprinkles if you like, and you’re done.
Grab Your Ingredients
- Cocoa powder: Use Dutch-processed cocoa for best results; it behaves differently than natural cocoa with leaveners.
- Neutral oil: Vegetable, canola, or sunflower oil keeps the crumb soft and moist for days.
- Buttermilk: Adds a slight tang and keeps the cake tender — particularly helpful because cocoa can dry baked goods.
Let’s Make This Sheet Cake
- Step 1: Preheat the oven to 350°F (175°C). Grease a 9×13-inch pan and line it with parchment, leaving an overhang for easy removal.
- Step 2: Whisk the dry ingredients together. In a separate jug, combine the wet ingredients except the hot water, then add to the dry mix and stir until smooth.
- Step 3: Gradually whisk in very hot water; the batter will be thin and pourable. This is normal and yields a tender cake.
- Step 4: Pour the batter into the prepared pan and bake about 35–40 minutes, until a toothpick inserted in the center comes out clean. Cool completely before frosting.
Different Frostings
If you’d like an alternative to chocolate-on-chocolate, try one of these frostings:
- Vanilla buttercream for a classic pairing.
- Biscoff buttercream for cookie-butter flavor contrast.
- Cream cheese frosting for a tangy complement to chocolate.
- Mint frosting for a refreshing twist.
- Oreo frosting for a cookies-and-cream vibe.
More Party Cakes
-
Easy & Simple Chocolate Cake with Vanilla Frosting -
Chocolate Chip Sheet Cake with Chocolate Frosting
-
Berry Vanilla Cake with Whipped Mascarpone Frosting
-
Easy Funfetti Oreo Cake with Oreo Frosting
Made This Recipe?
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Thank you!
Ella
Recipe
One Layer Chocolate Cake (Sheet Cake)
Ella Gilbert
Equipment
-
1 9×13-inch cake pan
Ingredients
Chocolate Cake
- ¾ cup (65 g) Dutch-processed cocoa powder
- 1 ¾ cups (350 g) granulated sugar
- 2 cups (220 g) all-purpose flour
- 2 tsp baking soda
- 1 tsp baking powder
- ¾ tsp kosher salt
- 2 eggs, room temperature
- 1 cup (240 ml) buttermilk, room temperature
- ½ cup (120 ml) vegetable oil
- 1 cup (240 ml) very hot water
Chocolate Sour Cream Frosting
- ½ cup (110 g) unsalted butter, room temperature
- 1 cup (113 g) confectioners’ sugar
- ½ cup (42 g) Dutch-processed cocoa powder
- ¼ cup (60 ml) sour cream, room temperature
- 3 oz (85 g) dark chocolate, chopped and melted
- Pinch kosher salt
Instructions
Make Cake
- Preheat the oven to 350°F/175°C. Grease a 9×13-inch pan and line with parchment, leaving an overhang to lift the cake out easily.
- Whisk together flour, cocoa powder, sugar, baking powder, baking soda, and salt in a large bowl.
- In a jug, whisk buttermilk, oil, eggs, and vanilla. Pour into the dry ingredients and mix until just combined.
- Slowly whisk in very hot water; the batter will be thin. Pour into the prepared pan.
- Bake 35–40 minutes, until a toothpick inserted in the center comes out clean. Cool in the pan 10 minutes, then transfer to a rack to cool completely.
Make Frosting
- Melt the chopped dark chocolate gently (microwave in short bursts, stirring often) and set aside to cool slightly.
- Beat butter and confectioners’ sugar on low until combined, then increase speed to high and whip 2–3 minutes until light and fluffy.
- Add cocoa powder and beat on low, then medium for 1–2 minutes to incorporate.
- Add sour cream, melted chocolate, and a pinch of salt. Mix until smooth. Spread over the cooled cake.
- Slice and serve. Store tightly covered in the refrigerator for up to 5 days; bring to room temperature before serving.
Notes
These recipes were developed and tested using metric weights. Using a kitchen scale is recommended for the best accuracy. Cup conversions are provided but have not been directly tested.
Bring all ingredients to room temperature before starting, including sour cream.
Cake pan: Use a 9×13-inch pan with taller sides (not a quarter-sheet); this recipe fills the pan well.
Salt: If substituting fine salt for kosher salt, halve the amount (1 tsp kosher = ½ tsp fine salt).
Buttermilk: If you don’t have buttermilk, substitute equal amounts of sour cream or full-fat yogurt. To make a quick buttermilk substitute, add 1 tbsp lemon juice to 1 cup milk and let sit 5 minutes.
Sour cream for frosting: Full-fat Greek yogurt may work as a substitute, though this frosting was developed with sour cream.
Storage & make-ahead: Wrap cooled cake tightly and refrigerate up to 2 days or freeze up to 2 months. Thaw and bring to room temperature before frosting.
Carbohydrates: 65 g
Protein: 6 g
Fat: 24 g
Nutritional information is an estimate per serving and not guaranteed to be exact.