Southern Chocolate Mayo Cake is a classic 9×13 chocolate cake that stays moist and tender in a way that feels old-fashioned in the best sense. It’s the kind of cake I make when I want something reliable and chocolatey without a lot of fuss.

The mayonnaise doesn’t make it taste “mayo-y” at all—it just makes the crumb extra soft and keeps the cake from drying out. With a thick layer of cocoa buttercream on top, it’s rich, simple, and exactly what I want with a glass of milk or a cup of coffee.

I like this one for potlucks, Sunday dinners, and anytime I need a chocolate cake that slices neatly and holds up well on a dessert table. It’s also a nice option when you want an easy chocolate cake that still tastes homemade.

Pin This Recipe For Later!

Why You’ll Love This Recipe

No mixer needed: The cake batter comes together quickly with a whisk and a spoon, which is exactly what I want for a casual sheet cake.

Moist crumb: Mayonnaise gives the cake a soft, tender texture that stays that way even the next day.

Deep chocolate flavor: Cocoa in the cake and cocoa in the frosting makes it taste unmistakably chocolate, not just “sweet.”

Easy to slice and serve: A 9×13 cake is simple—frost it, cut it, and you’re done. No stacking or decorating stress.

Great make-ahead dessert: This is one of those cakes that’s just as good (sometimes better) after it sits for a bit.

Ingredients You’ll Need

Chocolate Mayo Cake

All-purpose flour: I use regular flour here. Measure it the simple way—spoon it into the cup and level it off so the cake doesn’t get heavy.

Granulated sugar: This is a straightforward, sweet Southern-style cake. It also helps keep the crumb soft.
Unsweetened cocoa powder: Use the cocoa you like to bake with (natural cocoa is totally fine). If your cocoa is lumpy, whisk it well so you don’t get little bitter pockets.
Baking soda: Don’t skip it—this is a big part of the rise in a mayo cake.

Baking powder: A little extra lift helps the cake bake up evenly in a 9×13 pan.
Kosher salt: It makes the chocolate taste more like chocolate. If you only have table salt, use a little less.

Mayonnaise: I strongly prefer full-fat mayonnaise here. Light mayo can work in a pinch, but the texture is better with the regular kind.

Warm water: Warm liquid helps the cocoa bloom a bit and makes the batter smoother. Warm brewed coffee works great too if you want a deeper chocolate flavor.
Vanilla extract: Just enough to round everything out. I use pure vanilla, but use what you have.

Chocolate Buttercream Frosting

Unsalted butter: Make sure it’s softened so it beats up smooth. If it’s too cold, you’ll fight little butter lumps.

Unsweetened cocoa powder: Same note as the cake—whisk out any lumps first. It keeps the frosting from looking speckled.
Powdered sugar: This is what gives you that classic thick buttercream. If it’s extra clumpy, sift it or just beat a bit longer.
Milk: This is your texture control. Start with what the recipe calls for, then add a splash if you want it looser and easier to spread.

Vanilla extract: Chocolate frosting still needs a little vanilla. It keeps the flavor from tasting flat.
Salt: Just a pinch makes a difference, especially with a sweet frosting.

Recipe Instructions

Preheat the oven: Heat the oven to 350°F. Grease a 9×13-inch baking pan, and line it with parchment paper if you want easier lifting and cleaner slices.

Mix the dry ingredients: In a large bowl, whisk the flour, sugar, cocoa powder, baking soda, baking powder, and salt until everything looks evenly mixed.
Add the wet ingredients: Add the mayonnaise, warm water, and vanilla. Stir until the batter is smooth and you don’t see dry flour pockets.
Bake: Pour the batter into the prepared pan and bake for about 35 minutes, or until a toothpick in the center comes out clean or with a few moist crumbs.

Let cool: Cool the cake in the pan until it’s completely room temperature. If it’s even a little warm, the frosting will melt and slide.

Make the frosting: Beat the softened butter until smooth. Beat in the cocoa powder, powdered sugar, milk, vanilla, and a pinch of salt until fluffy, adding a splash more milk if needed.
Frost and serve: Spread the frosting over the cooled cake. Slice and serve.

Some of my tips!

This is the part that really makes a difference. If you only read one section, make it this one because this is where I share the little trick that helps the recipe turn out so well.

Recipe Tips & Tricks

Use full-fat mayonnaise. It really does make a difference in the texture. The cake comes out softer and more tender.

Mix just until smooth. Once you don’t see dry streaks, stop stirring. Overmixing can make a sheet cake bake up a little tougher than it needs to be.

Try warm coffee instead of water. It won’t make the cake taste like coffee, but it does deepen the chocolate flavor. I do it anytime I have a little leftover coffee sitting around.

Let the cake cool completely before frosting. If the pan still feels warm, wait. Warm cake + buttercream turns into a slippery mess.

Add milk slowly in the frosting. A small splash goes a long way. I like the frosting thick enough to hold swirls but still easy to spread.

Make some touches!

There are plenty of easy ways to serve this depending on the occasion. Keep it simple, or add a few small touches to make it feel a little more special.

Serving Suggestions

Milk: A cold glass of milk is simple and classic with a chocolate sheet cake. I like this best when the frosting is nice and thick.
Coffee: This is really good with coffee, especially if you used coffee in the cake batter. Even plain drip coffee works fine here.

Fresh berries: Strawberries or raspberries on the side are nice if you want something a little lighter on the plate. I usually keep them plain or lightly sweetened.
Ice cream: Vanilla ice cream with a square of this cake is a good, straightforward dessert. If you like a colder frosting, serve it slightly chilled.

Save it for later

This section covers how to store leftovers and what parts of the recipe you can prepare ahead of time.

Storage and Make Ahead

Store the cake covered at room temperature for up to 2 days. I usually keep it right in the pan with a tight cover so the cake stays soft.

For a longer hold, refrigerate the cake for up to 5 days. Let slices sit at room temperature before serving so the frosting softens back up.

You can make the frosting ahead and keep it in the fridge, then bring it to room temperature and beat it again until fluffy. If it feels stiff, add a tiny splash of milk.

A few quick answers

This section covers a few extra details that may help before you head to the recipe card.

Recipe FAQs

Does chocolate mayo cake taste like mayonnaise?

No. It just tastes like a rich chocolate cake. The mayonnaise is there for moisture and tenderness, not flavor.

Can I use coffee instead of warm water?

Yes, warm brewed coffee is a great swap. I do it when I want the chocolate flavor a little deeper, especially if I’m serving this to grown-ups.

Can I make this as a layer cake?

Yes. Bake the batter in two greased 9-inch round pans for about 28 to 32 minutes, then cool completely before frosting. The layers are fairly tender, so be gentle when turning them out.

How do I know when the cake is done?

A toothpick in the center should come out clean or with a few moist crumbs. If you see wet batter, give it a few more minutes and test again.

Before you go, take a look at a few other recipes below the recipe card. They use similar ingredients in a different way and are worth saving too.

Southern Chocolate Mayo Cake

Moist Southern-style chocolate cake made extra tender with mayonnaise and topped with classic cocoa buttercream

No ratings yet

PRINT PIN RATE

Prep Time 15

Cook Time 35

Total Time 50

Servings 12