Perfect Swiss Meringue Buttercream for 7-Layer Rainbow Cake

Make a rainbow cake with all seven colours of the rainbow. A simple, easy butter-based vanilla cake that tastes great, light, and fluffy. Frosted with my amazing Swiss meringue buttercream with chocolate drizzle. Then top with the kids’ favourite sweets.

Nothing’s more exciting than having your kids’ birthday party treat be a rainbow cake. This was my son’s birthday cake. My kids get many cakes since their mom is a decorator of cakes. I was given very strict specifications; the most prominent that it had to be seven different colors. As a matter of fact, with the kids around, I may have placed one color in the wrong order.

Why make this recipe?

• But here, in the video, this is just simple, easy, and quick. I added the buttermilk to my butter-based vanilla cake mix for a soft crumb.
• This is a 6-inch cake with seven layers, but you can also do it in six layers and leave out the indigo layer, really. Because the truth is, you can make as much amount of levels. Even a three-layer rainbow cake is going to be great.
• I used Swiss meringue buttercream, but you can use Italian meringue, American, French, or German buttercream-just whatever icing you like.
• Now, about the drip cake candy-it is totally up to you. Use any kind of candy that you like. Here, I used cheap lollipops because my son wanted a colorful cake. In the shop where I went to buy lollipops, my kids chose some with the most striking colors. So I picked them up.

Ingredients and substitutes

• All-purpose flour – for this tall cake, I use all-purpose flour to give it some rigidity in the layers.
• Butter – unsalted butter I prefer, because it allows me to control the amount of salt. If you have salted butter, that is totally fine, too; skip the salt for this recipe.
• Sugar: White sugar gives the colours of the rainbow vibrancy and niceness. Brown sugar tastes nice, but to show the true colours of this cake, white sugar does its magic here.
• Buttermilk: Bring in freshness to the cake’s tender crumb. You can make you’re own buttermilk in about 5 minutes, or you can buy them from the shop.
• Vanilla – Always use good quality vanilla. Preferably, you should use clear vanilla extract or vanilla sugar to keep the brightness and appeal of colors. But vanilla extract works absolutely great, too.

Step-by-step: 7 Layer Rainbow cake

Rainbow Cake Layers

• Preheat oven to 350° Fahrenheit (175° Celsius). Grease and flour seven 6-inch round cake pans.
• In a bigger bowl, whisk together flour, baking powder, baking soda, and salt.
• Cream the butter and sugar until light and fluffy in a large mixing bowl. Add eggs and beat one at a time. Finally, stir in the vanilla essence.
• Gradually add the dry ingredients, alternating with the buttermilk, until just combined.
• Divide the batter evenly between seven bowls. Tint each bowl of batter with gel food colouring, creating a rainbow of colours.
• Divide each coloured batter evenly between prepared pans and smooth the top. Insert a toothpick into the centre; if it comes out clean after baking for 15 to 20 minutes, it is done.
• Let the cakes cool in the pans for 10 minutes before removing them from the pans and transferring them to a wire rack to cool completely.

Swiss meringue buttercream

• Whisk the egg whites and sugar in a heatproof bowl. Set over a pot of simmering water, not letting the bottom of the bowl touch the water.
• Heat mixture, whisking constantly, until the sugar has dissolved and temperature of mixture reaches 160°F (71°C).
• Remove bowl from heat and beat with electric mixer on high speed until stiff peaks form and mixture has cooled, about 10 minutes.
• Add the softened butter in a few tablespoons at a time, beating well after each addition. Mix in the vanilla extract, then beat until the buttercream is smooth and creamy

White chocolate rainbow drip

• Melt white chocolate chips in a heatproof bowl set over a pot of simmering water or in the microwave.
• Divide the chocolate that has melted into separate bowls coloured with a different colour gel food colouring. Pour each coloured chocolate into piping bags.

Assemble

• Being frosting each layer, one at a time, with Swiss meringue buttercream.
• Stack the different colored layers of cake and frost the outside with just a thin coating of buttercream to give it a crumb coat.
• Refrigerate the cake for 30 minutes. Once chilled, frost the cake with remaining buttercream, smoothing the edges and top.
• Pipe tinted white chocolate drips along edges of the cake, letting them drizzle down the sides. Top cake with remaining colourful choc drips.
• Rest in refrigerator until time to serve.

Tips for Success

• At Room Temperature: Take the butter, eggs, and buttermilk out of the refrigerator and let them come to room temperature. This will ensure that these items can blend together well and creamily.
• Even Layers: Take the time to measure your batter for each cake layer using a kitchen scale to ensure even baking.
• Cooling Time: Let your cake layers take enough time to cool down completely. This way, they will not collapse during assembly, and the buttercream sets better.
• Chilling the Cake: After the crumb coat, the cake needs to be refrigerated for at least 30 minutes. That would set the buttercream and provide a firm base for the decoration of the cake.
• Smoother Frosting: You could achieve smooth frosting on your cake using either a bench scraper or offset spatula dipped in hot water to smoothen out the buttercream.
• Refrigerate the completed cake to assure the best texture and flavour, but let it reach room temperature before serving.
• White Chocolate Drip: Pipe the coloured white chocolate drips, starting at the top rim of the cake; start piping by gently squeezing the piping bag to allow a drip effect. Apply longer or shorter pressure for longer or shorter drips.
• Decoration: To make the rainbow theme pop even further, add more decorate on the cake. One could add sprinkles, edible glitter, or fondant for this.

FAQs