Organic Rainbow Cake with All-natural Homemade Food Coloring

Round rainbow cake

About two years ago I kept seeing all those neon rainbow cakes on Pinterest, and they looked great, but also looked packed full of fake chemical based food dyes. So, I set out to make a healthier, all-natural version with homemade food dyes vs. Red #40, Yellow #5 and such.

  • Recipe: Rainbow cake with vegan vanilla bean frosting - good for birthday parties!

  • Suitable for: Vegetarians - *See note for vegans below. The cake is vegetarian and the frosting is vegan.

  • Time needed: Ample. This is not a fast project.

NOTE FOR VEGANS: When I first made this cake I was not yet vegan. You can easily make a vegan rainbow cake though using the same method, just switch out the cake recipe below (which has eggs) for an eggless version.

Square rainbow cake

Cake Ingredients

  • 5 large organic egg whites at room temperature

  • 3/4 cup organic milk at room temperature - I used almond milk before too and it worked well

  • 2 and 1/4 teaspoons pure Fair Trade certified organic vanilla extract

  • 2 and 3/4 cups organic white flour, sifted (or other flour of your choice)

  • 1 and 3/4 cups organic granulated sugar

  • 1 tablespoon + 1 teaspoon baking powder

  • 3/4 teaspoon salt

  • 12 tablespoons unsalted organic butter, softened and cut into cubes (I have not tried this with vegan butter, so do so at your own risk)

Vanilla Bean Frosting Ingredients

  • 3 sticks + 2 tablespoons of organic butter - unsalted regular butter or vegan butter will work

  • 2 teaspoons pure organic Fair Trade vanilla extract

  • 3 cups organic powdered sugar

  • 3 tablespoons almond milk

  • Pinch of salt

  • 1 organic vanilla bean – scraped – optional

One idea - layer like-minded colors instead of rainbow colors - like this pink, white and violet cake

STEP 1: Make Your Homemade Food Coloring

To learn how to make homemade all-natural food dyes, read: Homemade food coloring for baked goods.

You'll need at least 3-4 different food dyes, but you can make as many or as few color layers as you like. In the case of the cake you see above, I used about 2-3 TBS of homemade food dye for each cake layer. Results with all-natural food dyes varies, but to give you an idea, here's what I used to color one 3/4 scoop of batter.

  • Bright green – 2 tablespoons spinach juice

  • Lighter green – 2 teaspoons green tea powder

  • Dark pink – 1 and 1/2 tablespoons of beet puree

  • Bright yellow – 1 full dropper of yellow Chocolate Craft liquid food coloring

  • Peach / light yellow – 1 and 1/2 tablespoons of carrot puree

  • Purple – 2 tablespoons blackberry juice

  • Light pink – 1 tablespoon strawberry puree

  • Violet – 1 tablespoon raspberry juice

  • Dark blue – 2 and 1/2 full droppers of Chocolate Craft liquid food coloring

  • Dark blue/purple – 2 tablespoons of blueberry juice

  • Orange – 4 full dropper red + 1 full dropper yellow Chocolate Craft liquid food coloring

  • Light blue – 1 full dropper of blue Chocolate Craft liquid food coloring

You can make your food dye the day before if you like. Once you make your food dye, keep it in the fridge until you're ready to color your batter.

STEP 2 – Prepare Your Cake Pans

  • Lightly grease the bottom and sides of your cake pans with a dab of organic olive oil

  • Place cut pieces of unbleached parchment into your pans and grease the parchment a little, again with organic oil.

  • Dust the pans with flour.

  • Set pans aside.

NOTE: If you have to reuse pans, because you only have a few, be sure to re-grease and re-flour between each new layer you bake.

Whipping up cake batter

STEP 3 – Make the Cake Batter

  • Preheat your oven to 350°F.

  • In a small bowl, combine and stir the egg whites, 1/4 cup of milk, and the vanilla.

  • In a large bowl, combine all your dry ingredients together.

  • Add all of the butter and the other 1/2 cup of milk to the large bowl.

  • Mix the contents of the large bowl on low speed (or by hand) until just moistened. Increase your mixing speed and mix for about 2 minutes.

  • Scrape the sides of the bowl to make sure everything is mixed well.

  • Add your egg mixture from the small bowl in THREE separate batches to the large bowl, beating on medium speed for 20 seconds after each addition.

Colored cake batter in pans

STEP 4 – Color Your Cake Batter

Gather up the food dyes you made during step 1.

Grab some bowls and a spatula.

Divide your batter into equal parts. I.e. however many layers you're making.

In general, the following batter coloring rules apply…

  • Use about 1/4 cup (4 tablespoons) of food dye to color 2 cups of batter.

  • Use about 2-3 tablespoons of food dye to color 1 cup of batter.

  • Use about 1-2 tablespoon of food dye to color 1/2 cup of batter.

To color your cake batter, choose a food dye, and add one tablespoon of color to start. If the color is not bright enough, add another tablespoon, mix, see what it looks like, and if needed add more.

IMPORTANT: Your unbaked cake batter will almost always look WAY brighter than the baked layers, so use more food dye than you think you need.

If you have leftover food dye, which is likely, you can freeze produce purees and juices in ice cube trays. Put the cubes in a container and save them for the next time you make homemade vegan ice pops, smoothies or another rainbow cake, cookies or frosting.

Cake layers cooling on rack

STEP 5 – Bake the Cake

  • After you color all your cake batter, pour the batter into your prepared pans and bake for 14 to 20 minutes (depending on how hot your oven runs).

  • Watch the cake closely. You want to take the layers out of the oven the second you can insert a toothpick that comes out clean.

  • Let the cake pans cool on racks for 10 minutes.

  • Loosen the sides of the cake with a small silicone spatula and invert onto lightly greased wire racks.

  • Gently turn cakes right side up.

  • Cool completely.

Frosted cake

STEP 6 – Making Your Frosting

This frosting is EXCELLENT if you like very light, creamy and not too sweet vanilla frosting.

  • Use an electric mixer or hand mixer to whip the butter for about 5 minutes until it becomes very pale and creamy. Vegan butter won't become more pale, but it will get just as creamy as regular butter.

  • Add all your remaining ingredients and mix on low speed for 1 minute, then on medium speed for 6 minutes.

  • If you like, you can use some of your natural food dyes to color your frosting, or leave it white.

If you're not a huge fan of vanilla frosting, you can make this basic recipe without the vanilla and instead add lemon zest, or almond extract, or orange zest and orange extract, or flavor it as you see fit.

STEP 7 – Assemble and Frost the Cake

I'm not the best cake froster/cake decorator. But, below are some tips.

Frozen cake layers

  • Freezing cake layers before you frost makes it MUCH easier to frost a cake. I usually wrap each cooled cake layer in parchment, then freeze all the layers for a few hours before frosting. You don't have to do this, but it's very helpful.

  • Once your cake layers are frozen, level them off carefully with a sharp knife. Then brush the excess crumbs carefully off each layer.

Arrange your cake layers in a nice color order

  • Arrange the layers in a stack to see which color order the layers look good in.

Frost between layers

  • To make the layers stick together (i.e. frost in-between layers) place your first layer on a cake platter or piece of parchment. Plop some frosting on, spread the frosting out to the edges of the cake, place the next slice on top of the first layer and continue until you have as many layers as you like.

Once all your layers have frosting in between them you'll need to frost the sides and tops.

Use a lot of frosting to avoid crumbs showing through

  • First, trim the sides of the cake (if need be) to make the sides more even.

  • Now, smooth on a thin layer of frosting all over the cake to seal in crumbs.

  • Smooth on more frosting on the top and sides, then smooth it out as best as you can.

  • You can use a cake pastry scraper to smooth your frosting OR use a stiff piece of paper folded up to make it thick.

If you're not good at smoothing out frosting, add a swirl of different colored frosting on top to hide imperfections

STEP 8 – Cake Storage

  • This cake is best the first day, but still great for a couple of days after.

  • To store leftovers, place in a cake container or wrap tightly in foil (though this will mess up your frosting) and store at room temperature.

  • This cake can be refrigerated for up to 5 days.

  • Un-frosted cake layers can be frozen for up to 2 months.

Rainbow cake slices


Article and all images by Jennifer C