Easy One Bowl Chocolate Cake (9x13 pan)

A fluffy one bowl chocolate cake that cuts into 24 pieces. Top it with fudge frosting or any frosting you like.

When you need chocolate cake for a crowd, bake it in a 9x13 pan. You get 24 pieces from one cake, with no layers to stack or level. You can even bake it the day before.

This 9x13 chocolate cake comes together in one bowl. It uses oil instead of butter, so there's nothing to soften and nothing to cream. Mix the batter with a hand mixer, pour it into the pan, and it's in the oven in about 15 minutes.

If you've made my six inch chocolate layer cake, this one works differently. That recipe uses butter and is made using a traditional creaming method, which makes it sturdier for a layer cake. This one uses oil and one bowl, and it bakes up fluffier. It works well as a simple snacking cake or a single-layer cake, and it serves more people.

I frosted mine with fudge frosting, but this cake pairs well with many frosting flavors. If you want something different, choose any frosting you like from my list of options below.

Ingredients for a Chocolate Sheet Cake Recipe (9x13)

Everything in this cake is a pantry staple. The full amounts are in the recipe card. Here's what to know about the key ingredients.

• Cocoa powder. Look for cocoa powder labeled "Dutch processed" or "alkalized". That's what I tested this recipe with. I haven't tested natural unsweetened cocoa powder in this cake.
• Sour cream. The acidity and fat in sour cream make the crumb tender. If half a large tub has been sitting in your fridge since the last recipe that only needed a few spoonfuls, this is where it goes.
• Eggs. You need two large eggs plus one yolk. The extra yolk keeps the cake soft.
• Vegetable oil. The oil replaces butter, which lets the batter come together in one bowl. It also keeps the cake moist.
• Coffee. Brew it and let it cool before you start mixing. You won't taste the coffee. It brings out the chocolate flavor. 

Room temperature ingredients. Take the eggs and sour cream out of the fridge ahead of time. Room temperature ingredients mix into the batter more evenly.

How to Make a 9x13 Chocolate Cake

Start with the pan. Grease the bottom and sides of a 9x13 metal pan with butter. Line the bottom with parchment paper, then grease the top of the parchment too. Preheat the oven to 350°F with a rack in the center.

In a large bowl, sift or whisk together the flour, cocoa powder, sugar, baking powder, baking soda, and salt. Keep going until the dry ingredients are evenly mixed.

Add the wet ingredients to the same bowl: the oil, eggs, extra yolk, vanilla, and sour cream. Mix with a hand mixer for 1 to 2 minutes, until everything looks incorporated. Scrape down the sides and bottom of the bowl with a spatula so nothing is left unmixed.

Turn the mixer to low speed and pour in the coffee slowly, mixing just until it's incorporated.

Finish with a few strokes of the spatula to make sure the batter is even and smooth. The cake batter will be very liquid. That's how it should look.

Pour the batter into the prepared pan, and it's ready to bake.

How Long to Bake Chocolate Cake in a 9x13 Pan

Bake the cake at 350°F for 28 to 32 minutes. I tested this recipe in a metal pan. I haven't tested it in a glass pan. If you use glass, I suggest lowering the oven to 325°F and baking it 5 to 10 minutes longer.

How Can I Tell If Chocolate Cake Is Done?

Chocolate cake doesn't turn golden brown, so you can't judge it by color. Start checking at the low end of the bake time. Insert a toothpick into the center of the cake. It should come out with a few moist crumbs. The edges should pull away slightly from the sides of the pan, and the top should spring back when you press it lightly. If the toothpick comes out wet, bake it a little longer and check again.

Should You Frost a Cake in the Pan?

The simplest option is to frost it right in the pan. I turn mine out because cutting slices in a metal pan scratches it, even with parchment underneath.

Let the cake cool in the pan for 10 minutes. Run a knife around the edges, then turn the cake out onto a wire cooling rack and remove the parchment. Let it cool completely, about 1 hour. Cooling times can vary.

Once it's cool, flip the cake right side up onto a platter or cake board and frost it.

If you'd still rather frost and serve the cake in the pan, skip turning it out. Let it cool completely in the pan, then frost it there. If you share my concern about scratching the pan, here's an option that I have not tested.

Turn the cake out to cool on the rack as above. Then flip it right side up onto a cake board cut to fit the pan, and lower the board and cake into the pan together. Frost it there. When you cut the cake, your knife hits the board instead of the metal.

Frosting Options for Chocolate Cake

The fudgy chocolate frosting in the recipe card is not your only option. Choose from any of your favorite flavors. You need about 2 cups of frosting to cover the top and sides of this cake. If you use a different recipe, check its yield and make more if it comes up short.

• Vanilla buttercream gives you a chocolate and vanilla cake for birthdays and parties.
• Cream cheese frosting adds a little tang against the chocolate.
• Salted caramel frosting brings a sweet and salty contrast.
• Strawberry buttercream makes it a chocolate strawberry cake.
• Peanut butter frosting turns it into a chocolate peanut butter cake.
• For Halloween, try black frosting.

Storing and Freezing

If the cake has a butter-based frosting, like fudge frosting, store it covered at room temperature for 1 to 2 days. For longer storage, keep it in an airtight container in the fridge for up to 5 days. A cake with cream cheese frosting always goes in the fridge.

To freeze the unfrosted cake, wrap it tightly in two layers of plastic wrap and freeze for up to 1 month.

To freeze a frosted cake, place it in the freezer uncovered for about 20 minutes, until the frosting feels firm. This keeps the plastic wrap from sticking to the frosting. Then wrap the cake in plastic and store it in an airtight container for up to 1 month.