Learn how to make a Rainbow Cake from scratch. With super-easy frosting technique no complicated piping and spreading needed. Rainbow colors inside and around the cake. By the way, have you seen my colorful Strawberry Vanilla Cake with red hearts in it?
To make the cake layers, mix egg whites and salt until soft peaks form. Add sugar and mix until glossy and stiff.
Then separate into 7 bowls equally and color with violet, indigo blue, blue, green, yellow, orange, and red. Take as much coloring as desired. Mix just until evenly colored. The more color you use, the more intense and darker the layers are. Less coloring leads to a pastel tone. Read the instruction on the package if you are not sure how much to use. I recommend using gel or paste coloring.
Then fold in almond flour and flour.
Draw seven 8" circles on parchment paper and flip over the paper. Spread meringue into the drawn circles till the outer edges.
Don't bake the meringue too long to prevent them from browning too much. Too much browning affects the color of your cake. Remove from oven when dry to touch. After baking immediately remove the baking paper and let cool to room temperature.
After mixing the butter, powdered sugar, marshmallow cream, and salt separate the frosting into 8 bowls. Color again with violet, indigo blue, blue, green, yellow, orange, and red.
Color the 8th bowl with blue to finish the cake on top with sky blue. Maybe you need to add a bit of white coloring to brighten up the color.
If you don't want to have a blue frosting on top, then separate the frosting just into 7 bowls and color with the rainbow colors.
When you color the frosting, place the cake layers next to your bowl and add the coloring little by little to reach the same tone of your cake layers. If your frosting is accidentally more colorful or darker as the cake layer, add a bit of white coloring to brighten up the color again.
The following frosting technique is a simple way to get the rainbow stripes around the cake without piping and spreading the frosting.
Place a closed 9" springform ring on a cake plate or stand. Place the violet meringue cake layer in the middle of the ring. Spread a bit of frosting underneath that the cake layer doesn't move around while frosting. Remember, the cake layers have a size of 8".
Then spread the violet frosting on top of the cake layer and till the edges of the springform ring that the bottom is evenly covered. Watch out that you don't color the inside of the ring higher than the violet layer ends if you want to have straight lines on the sides. The accuracy of your work affects the shape of the lines on the sides of your cake.
I didn't work that accurately because I love how the colors blend into each other. But it's up to your preference. Then chill at least 4 hours or overnight before removing the ring.b
After chilling remove the ring. For the best results, run an icing spatula around the sides before removing. This makes sure that no frosting sticks to the ring while removing. Press the spatula outwards against the ring while running around the sides.
If necessary, level the sides of the cake with the spatula. Do this by planting the spatula on one side of the cake uprightly and spin around the cake. Do this without pushing too much against the cake.
I decorated my Rainbow Cake with super fluffy meringue to get the most beautiful cloud shape on top. If you don't want to decorate yours with meringue, replace it with whipped cream, or marshmallows, and sprinkles.
To make this super fluffy and cloud-like meringue, combine egg whites, sugar, and water in a heat-proof bowl. Then place the bowl over simmering water and mix until stiff peaks form. This will take about 10 minutes. Then remove from heat and mix additional 5 minutes until cooled.
Pipe meringue in back and forth movements on top of the cake to create an irregular shape of a cloud.
Rainbow Cake Recipe
OPTIONAL: Meringue for decoration (or replace with whipping cream, marshmallows, or sprinkles)
- 4 large egg whites
- 2 cups caster sugar (400g)
- ¼ cup cold water (60ml)
- Preheat oven to 320°F (160°C).
- With a pencil, draw seven 8“ (20,3cm) circles on parchment paper. Then flip over the parchment paper and place on baking sheets.
- In a large mixing bowl with a handheld or stand mixer fitted with a whisk attachment, whisk egg whites and salt on medium-high speed until soft peaks form. Add sugar and whisk until glossy and stiff peaks form. Separate into 7 bowls equally. Color with violet, indigo blue, blue, green, yellow, orange, and red. Use as much gel or paste food coloring to your preference. Stir on medium-high speed just until combined and evenly colored.
- With a wooden spoon fold into each color 4 tablespoon of almond flour and 1 tablespoon of flour carefully. Equally spread the meringue into the drawn circles till the outer lines. Make sure that they are almost the same in size and thickness. Bake one layer at the time for 17-20 minutes until dry and not too browned (very lightly browned is ok). Remove from the oven when dry to touch. Immediately flip over the parchment paper and remove the paper. Let cool to room temperature.
- Mix butter with a handheld or stand mixer fitted with a whisk attachment on medium-high speed until creamy for about 2 minutes. Add about 1 + ½ - 2 cups sugar at the time and mix on low speed until combined. Add marshmallow cream and salt and mix to combine. Separate the buttercream into 8 bowls. Color with violet, indigo blue, blue, green, yellow, orange, and red in the same tone as your meringue layers are. Add white coloring to lighten up the colors if needed. Color the 8th bowl with blue and white to create a sky blue tone for the top of the cake.
Assemble the cake
- Place a closed 9" springform ring on a cake board or cake stand. Place the violet meringue cake layer in the middle of the ring. Spread a bit of frosting underneath the cake layer that it doesn't move around while frosting. Then spread the violet frosting on top of the cake layer and till the edges of the springform ring that the bottom is evenly covered. Watch out that you don't color the inside of the ring higher than the violet layer ends if you want to have straight lines on the sides. The accuracy of your work affects the shape of the lines on the sides of the cake. Repeat with indigo blue, blue, green, yellow, orange, and finish with red on top. Spread remaining sky blue on top evenly. Chill for 4 hours or overnight.
- OPTIONAL: Make the meringue: Fill a large saucepan ½ full with water and bring to a simmer over medium-low heat. In a heatproof bowl, whisk together egg whites, sugar, and water to combine. Place bowl oblique over the saucepan that the hot steam can escape around the sides of the mixing bowl. The bowl should not touch the simmering water. With a handheld mixer fitted with a whisk attachment, beat egg white mixture for 10 minutes or until shiny, glossy, and stiff peaks form. Make sure the meringue doesn't get too hot, or the egg whites will cook through, and the meringue will be lumpy. Remove from saucepan in-between to cool down a bit, if necessary. Not just that the meringue is lumpy in structure when cooked too hot, it also will smell and taste like cooked eggs whites instead like a meringue. Remove from heat and mix until cooled for about 5 minutes.
- Remove cake from the fridge. Run an icing spatula around the sides (push outwards against the ring while moving), open the springform ring and remove it. If necessary, level buttercream on the sides with the spatula by placing it on one side of the cake uprightly and spin around the cake without pushing too much against the cake. Pipe meringue with a piping bag fitted with a round tip on top of the cake. Go back and forth with the tip while piping to create an irregular cloud shape. Alternatively, decorate with whipping cream, marshmallows, or sprinkles on top instead of meringue if preferred. Store leftovers up to 3 days in the fridge.
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