Guest Post: Epic Rainbow Cake

Posted by: Site Administrator  :  Category: dessert

Here’s a post from my lovely wife on the birthday cake we made for our youngest this year…

Since I’ve had a number of comments along the lines of, “ooh, I want to do that now too!” here is a post full of things I learned while making the Epic Rainbow Cake.

I’ll start by saying I saw a pic online and said to myself, “Hey, that looks cool. I think I could do that!” And yes, I did. And it was more work than I expected. Whoops. Not horrible, but more than I expected.

Much of the work was in the dying and baking of the layers. I only had 2 pans, and had to make 6 layers. I figured I could do 2 at a time and be done fairly quick. This wasn’t the case. I had to cook each layer, then let it cool most of the way in the pan before taking it out, or else they fell apart. This slowed things down considerably.

To do over again, I’d either get more pans, and/or I’d get smaller pans to make each layer thicker. (see next point, and the one about leveling down below)

I first tried to take one single cake mix and divide it into 6, then bake 6 thin layers. That didn’t work so well. First, it didn’t bake all that well. Second, it was so thin that it just fell apart when I took it out of the pan. So, then I had to quick mix up another mix and recalculate each layer. If I had smaller diameter pans, I could have done it with a single mix and not had HUGE amounts of cake.
Here’s my first failed layer:

Here’s my first successful layer:

I used Wilton icing colors to make the rich color. (Like these.) They worked wonderfully. It took a lot of bowls and forks and knives, but it did the job well. I used forks for mixing each batch, as it seemed to mix the color in better. I used table knives to get the color from the jar into the cake mix. Amazingly enough, my hands aren’t rainbow colored today as I expected they would be. I think that’s more because I’ve washed them 3948573546 times in the last 26 hours than because I was careful not to get dye on me though.

I had some fun mixing the orange. I didn’t have orange dye, so I had to blend red and yellow myself.

This took a LOT more frosting than I expected. Of course, it was a lot more cake than I expected too.

Ok, on to actual instructions.

Some of the things you’ll need:
2 boxes white cake mix & whatever they call for to make the cake.
Wilton icing color, or similar strong food dye. (I woudln’t recommend using cheap liquid food dye for this. The amount you’d need would probably water down the cake badly.)
Bowls for each color

Start with two boxes of white cake mix. (I probably could have done something from scratch, but I wasn’t feeling that ambitious.)

Before mixing them, get out your kitchen scale and tare it with the mixing bowl on it. Then put all the cake mixes and the rest of what the cake mix calls for into the bowl and see how much it weighs. Then divide that number by 6 to know how much for each layer. (Our amount was roughly 11 ounces per layer, though each cake mix may differ somewhat.)

Mix them up according to package directions.

Scoop or pour out the amount of cake batter you need for each layer into separate bowls. Then add dye and mix thoroughly.

Bake each layer in a well greased 8″ round cake pan for 12 minutes [IB: Even the nonstick pans need a good coat of cooking spray. You really don’t want these to get stuck]. Test for doneness. Remove from oven and let cool before removing it from pan. Let cool completely before moving on to the frosting step. [IB: In to remove the cake from the pan without destroying it, find a plate that fits just inside the pan and put it face down on the top of the cake, flip it upside down while holding the plate. press the wire cooling rack against the bottom of the cake and flip it right side up again]

*I should insert here an instruction to level each cake as best you can. I didn’t do very well, and mine’s a bit dome shaped. If I had to do over again, I’d try to make each layer a bit thicker, and level it off better.

Mix up your frosting for the filling. I used cream cheese frosting in between each layer, and for my crumb coat. I used two 8oz packages of cream cheese, 1 stick of butter, all softened to room temp. Then added about 1 tsp vanilla and 3 cups icing sugar.  Mix well with stand or electric mixer.  This was BARELY enough, so I’d recommend adding at least another stick of butter and 1-2 cups of icing sugar, or just make more of whatever frosting you want to use. [ IB: It really helps to really crank the stand mixer speed to get ultimate creamy frosting – use the paddle, or one of these]

I frosted in between each layer. I’d have put more in between each, for a better visual effect, but I just didn’t have enough. Taste wise, it was a perfect amount though.

Then I did my crumb coat. A crumb coat on this is essential, unless you want multi-colored specs all through your white frosting. Let the crumb coat firm up in the fridge, or harden to the touch on the counter (depending on the type of frosting you use) for anywhere from 30 minutes to 2 hours. (I put mine in the fridge overnight, because it was late and I was too tired at this point. It worked fine to leave it overnight with the crumb coat, then finish frosting it the next day.)
Process pic of the crumb coat. See how I’m scraping frosting off the spatula to slap onto the cake? Yeah, I BARELY had enough.

For the outer layer of frosting, I used 1 1/2 sticks of butter, about a teaspoon of vanilla, 2 tablespoons of milk, and 3 cups icing sugar. This was BARELY enough to cover the outside well. Ideally, I’d have made more and had more to make the spreading on easier. (If you watch the videos from the crumb coat link above, it shows why having extra is good if you want it to look really nice.) I frosted the top, then the sides with a table knife. If I were going to do this more often than once every few years, I’d invest in a decent frosting spreader/spatula thing. (I’m sure they have a specific name… the videos I watched last night probably told me, but I’ve now forgotten.)

Personally, I liked it this way, plain white on the outside. I think it would lend more kick to the rainbow inside. However the birthday girl requested sprinkles, so sprinkles it was.

Fairly quickly before the icing was dry to the touch, I put the sprinkles on the sides. I had to work fast, because my icing was drying faster than I expected it to. I took a few sprinkles in my hand at a time and just threw them at the sides of the cake until I thought it looked good. Yes, truly. It was fun. And yes, I’ll be finding stray sprinkles in my kitchen for months. Especially since I spilled them in the process. See?

You can sort of see the big container of sprinkles there at the edge of the pic. Thankfully I’d washed my counters well before starting, so I could just scoop them up and toss them at the cake. I had to toss fairly hard to get them to stick because the frosting was drying. I’ve done this before with a different type of frosting and they stuck better, but it was a frosting that didn’t dry. (Cream Cheese frosting doesn’t dry. Buttercream does. Just fyi.)

This was the finished product:

I had hoped to have some extra frosting to color to pipe “Happy Birthday, C!” onto the top, but that was a no go. I had BARELY enough to cover the whole thing, and I was not going to mix up a third batch of frosting just to do some piping work. Plus, I was almost out of time as I had to go pick her up from preschool. So, the top stayed plain. I did stick candles into it for her so we could sing Happy Birthday to her, and so she could blow them out.

And here’s what it looks like to cut into:

And the first slice:

(Some of these were taken really quickly because I had a birthday girl and two of her friends wanting to eat the cake now please, so sorry if they’re blurry or not the best quality.)

Ok, I think that’s my full brain dump.  Sorry if it’s a bit disjointed, but I’m tired, and my brain is disjointed from the HUGE sugar crash I’m on right now. 🙂

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