naturally colored rainbow cake + bernie is one!!


Bernie is ONE!! Yes, it went by so quickly! Yes, she gets more delicious every day!! Yes, I began planning her vegetable-themed birthday party more than six months ago and spent hours and hours searching for the perfect garlands and outfits, hand drawing her invitations, developing new recipes, sketching out her table scape, typewriter-ing the seed packet party favors, and scheduling the prep down to the minute. (And yes, in retrospect, I see what Nick meant when he said that I am… crazy…) And then yes, we had to cancel it ☹️! But!! Even though we missed our fronds and family dearly, it was truly a magical beautiful Bernie day and we loved every single moment of it. We had sprinkle pancakes and blueberries for breakfast, homemade chicken and stars soup for lunch, and turkey spinach meatballs with freshly made fettuccine for dinner. In between, we played in pools of Cheerios and visited the farm cats. And then we had cake! Obviously!


I am so pleased with how this naturally colored rainbow cake turned out. It took a bunch of experimenting and tweaking to get the shades to match and to figure out a method that wouldn’t require too much fussiness/juicing/boiling of beets/etc. I tried using turmeric but that was too bright, and I tried using a store-bought precooked beet but that wasn’t bright enough and just got messy. In the end, I went with a combination of store-bought carrot juice, store-bought beet juice, and a big bunch of fresh mint. The cake is based on my go-to vanilla butter cake that is so incredibly moist, dense, and delicious. It’s one of my proudest cakes! The flavor of the beets and the carrots is undetectable and the flavor of the fresh mint shines through just a wee bit, enough to lend its herby flavor but it’s far from overpowering. I went with a basic cream cheese frosting to add some nice tang and decorated with Fimo clay cake toppers.

For Bernie’s mini cake, I stacked up the scraps that I cut off from leveling the layers and cut out tiny layers with a biscuit cutter. No separate cake pans necessary. I was so excited when I realized this would work! The cake is so moist that the scrap layers stuck together without a need for frosting between them. Bernie loved it! I took enough photos of her eating it to break my phone and she didn’t even make a huge mess which makes me think that one day she’ll make a great cook that will be good at the whole clean-as-you-go thing. 


Weeks ago, I baked the cake layers, let them cool, formed Bernie’s mini cake, wrapped everything in plastic wrap and froze them so that I could have one more thing checked off my to-do list for the party. It also made frosting them, especially the mini cake, way way easier. I always like to frost frozen cakes (and then allow to sit at room temperature for a few hours or overnight before serving). 

Important note about the layers! This cake was originally supposed to be three layers (pink, yellow, and green) but I added a blue layer at the last minute because we were going to be expecting more guests than my usual three-layer cake serves and also because I needed to test two of the layers again so figured I’d experiment with a blue layer for the third. The blue layer is not a part of the recipe below but if you’d like to make a blue layer, simply use the same method as the green layer but sub out the mint for wild blueberries (I used frozen). You’ll have to either add another third batch of batter (using a scale and weighted measurements will help with this and ugh sorry about the 1/3 of an egg thing!) or replace one of the other colors with the blue. I’m sorry for any confusion that this causes!!

Naturally Colored Rainbow Cake

Makes one 3-layer 8” cake (and a mini cake!)


3 1/2 c (450g) all-purpose flour

1 tb baking powder

1 1/2 tsp kosher salt

1 c (225g) unsalted butter, room temperature

1/2 c (112g) refined coconut oil, room temperature

2 1/4 c (450g) sugar

4 large eggs, room temperature

1 tb vanilla bean paste or extract

1/2 c (120g) sour cream, room temperature

1 c (236g) whole milk, divided

1/4 c carrot juice

1/4 c beet juice (storebought is fine, the one I get has a little lemon juice added and that’s ok)

1/4 c firmly packed fresh mint leaves


1 c** (225g) good quality unsalted butter, room temperature

8 oz (224g) cream cheese, room temperature

4 c** (480g) powdered sugar

1/8 tsp kosher salt

1 1/2 tsp vanilla bean paste or extract

3 tb** (45g) heavy cream

**if you’re making a mini cake, I recommend adding another 1/2 c of butter, 1 c of sugar, and 1 tb of heavy cream to the frosting in order to have enough!


To make the cake layers: preheat the oven to 350ºf. Grease and line the bottoms of three 8” cake pans with parchment and set aside. (For a 4-layer cake, which is the one on the pictures, please see my note above!)

In a large bowl, sift together the flour and baking powder, and then lightly stir in the salt and set aside.

In a stand mixer fitted with a paddle attachment, cream together the butter, coconut oil, and sugar on medium high for 3-4 minutes, until light and fluffy. Add the eggs, one at a time, beating well after each. Reduce the mixer to low and add the vanilla and sour cream. Gradually add the dry mixture and mix until about 80% combined (you’re going to continue to mix once you add the coloring so only partially mixing at this stage prevents over mixing the batter). Divide the batter evenly into 3 bowls (using a scale helps with this!). In the first bowl, add 1/4 cup of milk and the carrot juice and fold together until smooth and just combined. In the second bowl, add 1/4 cup of milk and the beet juice and fold together until smooth and just combined. In a blender, blend together the mint leaves with the remaining 1/2 cup of milk until very smooth. Add this to the third bowl and fold together until smooth and just combined. Transfer the batters to the cake pans and spread them out evenly. 

Bake until the edges of the cakes are lightly browned and a toothpick inserted into the center comes out with a few crumbs on it; begin checking for doneness at 30 minutes and try your darnedest not to let it over bake. Let in the pans for 10 minutes and then transfer to a wire rack to cool completely. 

To make the buttercream: 

In a stand mixer fitted with a paddle attachment, beat together the butter and cream cheese until creamy. Gradually add the powdered sugar, and then mix in the salt, vanilla, and heavy cream. Mix until creamy.

To frost the cake, level the top of the layers and then stack them up with a layer of frosting in between. (The cakes bake up generally pretty flat so there won’t actually be that much to level off.) Frost all over and decorate as desired.

To make a mini cake, stack the leveled scraps of cake up, give them a good firm pat so they stick, and cut out four 2 1/2 inch circles with a biscuit cutter. Don’t worry if some of the scraps tear, the cake is moist enough that when you stack up the scraps, they’ll all smoosh together. Stack them on top of each other and, if you have the time, wrap the cake tightly in plastic wrap and freeze for a few hours or even a few weeks. This will make frosting this tiny cake way easier! Frost while frozen and let come to room temp before serving.

This cake is super moist that you could definitely decorate the day before serving. Let it sit at room temperature overnight.

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