How to make Rainbow Cake

What You Need


Joshua John Russell’s vanilla cake recipe (available when you start your free trial )
Joshua John Russell’s Swiss Meringue buttercream recipe (available when you start your free trial )
Joshua John Russell’s white chocolate ganache recipe (available when you start your free trial )
India Tree food coloring
India Tree sprinkles
India Tree sanding sugar


Offset spatula
Round cake pans
Icing smoother
Rubber spatula
Piping bags
Open star piping tip
Revolving cake stand
Cake leveler (optional)
Small bowls for buttercream
Measuring cups


1. Bake the Cake

mint-colored electric mixer sifting white batter in clear mixing bowl

Prepare your natural vanilla cake batter as directed in the recipe. Divide it equally into four round cake pans, bake and cool completely.

Pro Tip

Before pouring the batter into the pans, prep ’em the all-natural way: with coconut oil and flour.

2. Color the Buttercream

top view of a big bowl of white buttercream surrounded by smaller bowls of rainbow colored buttercream

Whip up a batch of Swiss meringue buttercream and divide it into seven small bowls. Use the natural India Tree food coloring to dye each bowl a color of the rainbow — red, orange, yellow, green, blue, indigo and purple. You’ll have to mix some dyes together to get the colors you need.

Pro Tip

The reason we’re adding food color to the buttercream and not the cake itself? Natural food colors change when they’re baked — blue becomes gray, yellow becomes pink, etc. By coloring the buttercream instead, we get more control and a nice, vibrant look.

3. Level

leveling a cake by using a knife to cut off the top while on a cake stand

Once the cakes are cooled, level the dome off the top and slice each in half to form 8 nice, flat layers.

4. Fill and Stack

round vanilla cake with purple buttercream spread on top

Place 1 cake on a cake stand and spread 1 cup of purple buttercream across the top. Place a second cake on top and cover that in indigo frosting. Keep stacking cake and spreading buttercream until you have the rainbow filling complete. Then chill the cake until firm.

5. Add a Crumb Coat

spreading white frosting on cake filled with rainbow frosting

Use a knife to shave down the cake’s sides until smooth. Then cover the entire cake with a crumb coat (a very thin layer) of white Swiss meringue buttercream. This doesn’t have to look perfect! Smooth the sides with a straight edge and chill the cake again.

6. Spread the Final Coat

circle cake with thick layer of white frosting being added to the sides and top

Add one more (thicker) layer of white buttercream. Smooth the edges just like before. (This also doesn’t have to look perfect!)

7. Add Color

Joshua John Russell smoothing a white cake and blending rainbow colors onto the buttercream

Dab food coloring onto your spatula and apply it to the cake surface in a stripe around the sides. Once all your colors are added, use a straight edge to blend and spread the color, while keeping the surface smooth, as shown in the video. As you work, move color up and down the cake to cover all the white space with an artistic, colorful finish. Scrape the top to level it when you’re done.

8. Sprinkle the Sprinkles

hands holding a colorful sprinkles mixture above a glass bowl

Mix together the India Tree sprinkles and sanding sugar in a bowl. Use your hands to press the sprinkles into the buttercream around the cake’s base. Chill the cake to make the sprinkles stick.

9. Pour On Ganache

spreading purple ganache over the top of a rainbow cake

Prepare white chocolate ganache as instructed in the recipe. Mix in food coloring and pour it over the top of your cake as shown in the video.

Pro Tip

Only use a few drops of food coloring — enough for a pastel hue. Adding too much color can cause the ganache to become too thick for the drip effect.

10. Finish with Rosettes

buttercream rosettes on top of purple ganache covered in sprinkles

Using a piping bag fitted with an open star tip, pipe Swiss meringue rosettes around the top of the cake. Then add a few more sprinkles to the top, and you’re done!

Author: Flourish Cakes

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