Looking for something fun and sweet this summer, celebrate with this watermelon buttercream cake! It’s perfect for a watermelon birthday party or a summer family BBQ! 

This watermelon cake starts with a fluffy watermelon scented cake that’s filled with a tart lime curd and creamy watermelon buttercream. Then it’s decorated to look like the sweet summer fruit which is the best part. Not only is this cake beautiful it’s beyond delicious! 

Since baking and cake decorating starts with confidence in the kitchen, this watermelon cake is great for beginner bakers. This watermelon cake uses basic buttercream techniques that will help you become a more confident baker. In this tutorial, I’ll give you all the tips and tools needed to replicate this cake at home. 

I’ll also walk you through how to work with fondant to create the black seeds. It’s a very simple process that will give you a head start working with fondant.  

Tips before baking: 

• You can bake the cake layers ahead of time. Simply wrap the cake layers in plastic wrap and freeze up to one month. 
• You can find watermelon candy oil or watermelon flavoring at your local cake specialty store or online like Amazon. 
• You can make the lime curd and buttercream a day ahead and refrigerate them overnight. Then take them out to come back to room temperature. Make sure the buttercream is at room temperature before re-whipping.
• A single batch of this cake recipe makes three, 6-inch round cake layers or two 8-inch round cake layers. Double the cake recipe to make enough cake batter for three, 8-inch cake layers.
• Be careful to not overmix this cake batter or else the cake will come out dense. Mix until all ingredients are well incorporated. 
• Food coloring gets darker over time so it’s best to gradually add the food coloring. 
• Serve cake at room temperature. 

What Tools You’ll Need to Make This Cake: 

• 3, 6-inch cake pans or 2, 8-inch cake pans
• Offset spatula 
• 8-inch or 10-inch white cake board 
• Serrated knife or cake leveler 
• Turntable 
• Bench scraper or cake scraper
• Piping bag (I use silicone reusable bags)
• Small fondant rolling pin 
• Small round cutter or small piping tip 
• Silicone fondant mat
• Whisk
• Rubber Spatula
• Non-Stick Cooking Spray and Parchment Paper
• Ice Cream Scooper with Trigger Release (for dividing cake batter evenly)
• Cake Stand, optional
• Leaf green gel food coloring 
• Neon green gel food coloring
• Fuschia gel food coloring
• Super red gel food coloring
• Watermelon candy oil or watermelon flavoring

Here’s how to make this watermelon cake perfect for summer! 

Let’s Get Baking! 

How to Make Watermelon Cake 

1. Preheat oven to 350 °F. Spray three 6-inch round cake pans or two 8-inch round cake pans with non-stick spray, line the bottom of each pan with parchment paper and spray again. Set aside.
2. In a medium-size bowl, whisk and stir together the all-purpose flour, cornstarch, baking powder, and salt. Set aside. 
3. In the stand mixer bowl fitted with a paddle attachment, beat the butter, oil, and sugar on medium-high for 5 minutes.
4. Add the eggs, one at a time to the stand mixer bowl and beat on medium until well incorporated.
5. Turn the mixer on low and add the flour mixture to the butter mixture until fully incorporated. 
6. Pour in the buttermilk and add the watermelon candy oil. Add a drop of fuchsia and super red food color to make a medium red color. Mix on medium for 30 seconds. Scrape down the sides of the bowl. 
7. Evenly distribute the cake batter among the three cake pans and bake for about 35-40 minutes or until a toothpick inserted into the center of each cake comes out clean or with just a few moist crumbs.
8. Remove cakes from oven and let cool in pans for 10 minutes before inverting onto cooling racks to cool completely. Wrap cakes in plastic wrap and place in the freezer to chill for 30 minutes. 

How to Make Lime Curd

1. In a medium saucepan, whisk together the whole egg, egg yolk, sugar, lime zest, and lime juice. 
2. Continue whisking over low-medium heat until the sugar has dissolved, about 5 minutes.
3. While whisking, add cold butter pieces one at a time. Continue cooking the mixture for 4-5 minutes until it’s thickened and coats the back of a spatula. 
4. Press plastic wrap directly on top to prevent a skin from forming. Refrigerate lime curd until completely set, at least 1 hour.  

How to Make Watermelon Buttercream 

1. In the stand mixer bowl fitted with the paddle attachment, beat the butter until light and fluffy, about 5 minutes.
2. Turn the mixer to low and gradually add the powdered sugar, followed by the heavy cream, salt, and watermelon candy oil. Mix until incorporated completely. Scrape down sides of the bowl. 
3. Turn the mixer to medium-high and beat the frosting for about 5 minutes until light and fluffy. 
4. Turn the mixer on low and mix for 2 minutes to push out any air bubbles. 
5. Divide the remaining buttercream into 4 bowls, three small bowls, and 1 medium bowl. In a medium bowl, color the buttercream first with a drop of fuschia food color to build a base color then add a drop of super red food color and a drop of soft pink to make a bright watermelon color. Fill ⅔ of a piping bag with the red buttercream and set aside for stacking. 
6. Continue to color the small bowls of buttercream. One small bowl will be dark green, the second small bowl will be neon green and finally keep the last small bowl the original light pink. 

Putting It All Together 

1. Remove the cake layers from the freezer and unwrap the cake layers. Next, use a serrated knife to cut off the dome of the cakes to make the layers flat and even. 
2. Add a small amount of buttercream onto the center of the cake board. 
3. Layer the chilled watermelon cake, cut side up onto the cake board. 
4. Place a thin layer of buttercream on top of the cake, then pipe a ring around the edge of the cake layer. Add 1/4 cup of lime curd inside the circle of buttercream. 
5. Place another cake layer cut side down over the top. Repeat process for another layer. Crumb coat and freeze for 20 minutes.
6. Starting from the bottom of the cake, add a row of dark green buttercream. Then add a row of neon green buttercream. Add a thin row of light pink buttercream. 
7. Next, add a thick layer of pink buttercream on the remaining part of the cake. Smooth the sides out using a cake scraper. Place the cake into the fridge to set the buttercream. 
8. To make the watermelon seeds, roll out a thin piece of black fondant on the silicone mat. Use cornstarch if the fondant is too sticky. Use a small round cutter or piping tip to cut out 18-24 circles. Then pinch and squeeze the circle to look like a teardrop shape. 
9. Place two rows of the black fondant seed on the red buttercream to complete the watermelon cake. 

This watermelon cake will certainly impress your friends and family. It’s perfect for kids of all ages! 

In the comments below, tell me what’s the #1 thing you’re struggling with baking and cake decorating? For real, though. I’m a real human being and read every comment I get. Don’t be surprised if I reply to a few of you! 🙂

You May Also Enjoy: 

• Ice Cream Cone Drip Cake (tutorial)
• How to Make Perfect Cake Pops (free training) 
• Common Baking Mistakes & How to Avoid Them (free ebook)
• How to Decorate Your First Cake (free course)
• Cake Decorating for Beginners (online course)

Happy Baking! 

Hey, if you liked this tutorial, you really should check out, Cake Decorating Creator Program, my online cake program. I coach you on everything I teach on these cake tutorials so that you can uplevel your baking and decorating skills. We 10x it so you get the results you want most. Like any new skill, it’s important to learn from the ground up to build a foundation, so you can take on any cake challenge. It is an investment your future self will thank you for. Check it out at XOKatieRosario.com/creator-program. I will see you there!

Watch The How-to Video Below: 

 

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