The BEST gluten-free chocolate sheet cake recipe, bar none. With a thick swirl of chocolate buttercream and festive sprinkles, this is the perfect gluten-free chocolate birthday cake.

We’re very mindful about letting Zoella (age 3) eat chocolate. We held off as long as we could and when I first gave her a taste, I thought she’d find it too bitter like I did as a kid, but that’s not the case. I even offered her a tiny piece of 90% extremely dark chocolate, but even that didn’t deter her. Now, she’s a chocolate bloodhound. If ever I sneak a bite of chocolate, she knows. 

Her: *sniff sniff* “I smell something.”

Me: “I just ate some _____(insert blatant lie).”

Her: “I smell chocolate.”

(Damn it). Now I know why my friend Emily texts me from the pantry floor where she hides from her kid to eat candy bars.

For her third birthday, she requested a “chocolate and vanilla cake with rainbow frosting” every day for a month. That’s exactly what I made as a four-layer cake, but when all 42 guests confirmed yes for her birthday party, I panicked and also made this gluten-free chocolate sheet cake at the 11th hour. 

I started with my favorite gluten-free chocolate cake recipe as a base. Except I hadn’t tested it as a sheet cake, so it came out too thin with not enough batter for the size of the pan. I panicked again and made another sheet pan of cake, stacking them together with a generous layer of chocolate buttercream between. I now had enough cake to feed an army. 

The best gluten-free chocolate cake

This gluten-free chocolate cake is so good that even with 2-3 servings per guest (including toddlers and newborns) almost all of it was gone by evening and we polished off the rest for breakfast.

I’ve shared the base of this cake before as a gluten-free chocolate layer cake and gluten-free chocolate cupcakes, but I don’t want you to make the same mistake I did when I first converted it to a 9×13 sheet cake. So I’ve adapted it accordingly. 

With a thick swirl of chocolate buttercream and plenty of festive sprinkles, this version is the perfect gluten-free chocolate birthday cake. No fussing with layers, crumb coats, or piping frosting. Just dump it in the pan, bake it, cool, then slather it in frosting.

Don’t forget to lick the spatula.

This cake is the best gluten-free chocolate cake recipe, bar none. I’d go so far as to call it the best chocolate cake ever as well. I’ve made it over 200 times, for every occasion: birthdays, baby showers, Valentines’ Day, Father’s day, dinner parties, I-just-need-cake days (you celebrate that too?). And every time, people ask for the recipe and no one suspects it’s gluten-free.

If you’re new to baking gluten-free and want a fool proof recipe that will blow people away, start with this cake, in any form. 

Gluten-free buttercream frosting

I’ve topped this cake with a creamy chocolate buttercream frosting that accentuates the classic chocolate cake flavor. A bit of milk or heavy cream keeps the frosting soft and smooth – perfect for spatula swirls. 

I always add a bit of chocolate extract to my chocolate desserts to boost the flavor, but if you don’t have any, just sub in more vanilla extract. 

How to make moist gluten-free chocolate cake

The great thing about this chocolate cake is that it doesn’t dry out quickly. With oil as the fat, this cake is light and fluffy with a moist chewy crumb. Even in the oven, it’s incredibly forgiving. When testing it with a toothpick, err on the side of just a little bit longer. To this day, have never accidentally over-baked it.

It’ll last for several days sealed in an airtight container – even with the frosting. Or, if you’re planning ahead, you can store the cake right in the sheet pan with a layer of plastic wrap or bee’s wrap overnight and frost the cake just in time for your party. 

To save you the trouble, here’s how you’d convert this gluten-free chocolate sheet cake into a layer cake or cupcakes. The same exact batter quantity below makes:

• 1 9×13 cake – bake for 45-55 minutes
• 3 8-inch layer cakes – bake for 33-37 minutes
• 36 cupcakes – bake for 18-22 minutes

Whatever form you prefer, this will become your go-to chocolate cake recipe!

More Gluten-Free Cake Recipes

• Gluten-Free Lemon Cupcakes
• Gluten-Free Vanilla Raspberry Cake
• Chestnut Plum Upside-Down Cake
• Spiced Banana Date Cake

Gluten-Free Chocolate Sheet Cake with Chocolate Buttercream

Yield: 1 9x13 sheet cake, 24 servings

Prep Time: 20 minutes

Cook Time: 50 minutes

Total Time: 1 hour 10 minutes

The BEST gluten-free chocolate cake recipe, bar none. With a thick swirl of chocolate buttercream and festive sprinkles, this is the perfect gluten-free chocolate birthday cake.

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Ingredients

Gluten-Free Chocolate Sheet Cake

• Scant 1 cup milk (1 cup minus 1 tablespoon or equivalent in buttermilk and skip the vinegar)
• 1 tablespoon white vinegar
• ¾ cup + 3 tablespoons (168g) sweet rice flour (such as Mochiko)
• ¾ cup (99g) gluten-free oat flour
• ½ cup + 1 tablespoons (84g) millet flour
• 1 cup + 2 tablespoons (128g) unsweetened dutch-processed cocoa powder, sifted (I use Rodelle Organic Cocoa)
• 2¼ cups (503g) organic cane sugar
• 2¼ teaspoons baking powder
• ¾ teaspoons baking soda
• 1½ teaspoon kosher salt
• 3 large eggs, room temperature
• 4½ tablespoons safflower oil (or other neutral vegetable oil)
• 1½ teaspoon pure vanilla extract (I use Rodelle)
• ¾ teaspoon chocolate extract (or ¾ teaspoon more vanilla extract) (I use Rodelle)
• 1 cup hot water

Chocolate Buttercream

• 1½ cups (12oz) unsalted butter, just about room temperature (60-70 degrees)
• 4½ cups (563g) powdered sugar
• ¾ cup (85g) unsweetened dutch-processed cocoa powder, sifted (I use Rodelle Organic Cocoa)
• ½ teaspoon kosher salt
• 2½ teaspoons vanilla extract
• ¾ teaspoon chocolate extract (or ¾ teaspoon more vanilla extract) (I use Rodelle)
• 3-4 tablespoons whole milk or heavy cream
• Optional: Festive sprinkles

Instructions

1. Preheat the oven to 350°F. Prepare a 9x13 cake pan by lightly oiling it, and lining it with parchment paper.
2. If not using buttermilk, combine the milk and vinegar in a small cup and let sit while you measure the flour, at least 5 minutes.
3. In a large bowl, sift together the sweet rice flour, oat flour, millet flour, cocoa powder, sugar, baking powder, baking soda, and salt.
4. In the measuring cup, whisk the milk and vinegar mixture with the egg, oil, vanilla extract, and chocolate extract until smooth. Pour this mixture into the dry ingredients and stir lightly. Pour the hot water into the dry ingredients and mix until completely smooth, scraping up the sides and bottom to completely incorporate.
5. Pour the batter into the prepared cake pan and bake for about 45-55 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs and the center bounces back when poked. In my experience, it's best to err on the side of an extra minute or two to be sure - this cake is very moist and won't over-bake very easily.
6. Let cool in the pan for 10 minutes, then overturn the cake onto a wire rack to cool completely. To do this, I place a large sheet pan over the baking pan and, holding it together, carefully flip the cake to release. Peel off the parchment paper, then place a wire rack over the top, and carefully flip right side up.
7. While the cake cools completely, prepare the frosting. In the bowl of a stand mixer fitted with the paddle attachment, cream the butter over medium speed.
8. Sift together the powdered sugar, cocoa powder, and salt. Slowly add this to the butter, in 4 batches, beating until incorporated. Add the vanilla and chocolate extracts and mix until smooth. Add the milk or cream, starting with just 2 tablespoons and adding additional milk or cream as needed, until frosting is smooth and spreadable. It should be somewhat glossy, but still hold swirls.
9. When the cake has cooled, swirl the buttercream over the top of the cake (I recommend using the back of a soup spoon) and top with colorful sprinkles, if desired. Slice into 24 pieces and devour.