Rainbow Cake Recipe

A number of people asked for the recipe I used for the monster birthday cake I made myself.... this one:

I must give credit, where credit is due:

I saw this cake on MckMama's blog about a year ago or so. She'd had a get together with friends and someone made this cake. It blew her away. And I thought the pics were stunning. I stuck the idea in the back of my mind and thought one day I'd try that... Then, last week, I decided that day had come :)

So I googled rainbow layer cake. And found out that the recipe originates back to a college student who goes by the blogger name "Whisk Kid." You can read her whole post, and original recipe HERE. But if you want to know how I did it, in more detailed steps - and with the tweaks I made, keep reading below:

I liked the idea of the rainbow cake. But if I was going to do it, I wanted the layers to stand out more than they did on Whisk Kid's cake. So I altered the recipe - I increased it by 50%. And I'll tell you, if you have a stand mixer - use it! It gets hard to mix by hand. And the batter will fill that stand mixer bowl about as full as you want it before you need to stop mixing for fear of making an overflowing mess.

I also added vinegar to the recipe, because I did not have gel food coloring in all the colors (just blue, yellow & green). Whisk Kid recommends you use gel because the food coloring liquid drops will not turn out vibrant. What she fails to mention is that the food coloring liquid drops do become vibrant, if they have an acid to play off of. So I added a Tablespoon of vinegar to the milk. No, you can't taste it. But can you agree, my red, orange & purple colors are vibrant ;-)  As much so as the green, blue & yellow that were made with gel!

Ok... on to the recipe I used:

RAINBOW LAYER CAKE BATTER:

3 sticks butter, room temp
3 1/2 c white sugar
7 large egg whites, room temp
3 teaspoons vanilla
4 1/2 c flour
6 tsp baking powder
3/4 teaspoon salt
2 1/4 c milk, warmed for 30 sec in microwave to bring to room temp
1 Tablespoon of white vinegar
Food coloring
 
In a large bowl, mix together flour, baking powder and salt. Set aside.
 
Then, in your mixer, cream butter & sugar together. Add the egg whites slowly. Then add vanilla till well mixed.
 
Next, add the vingar to your milk (don't pour in batter yet). The milk will probably curdle slightly - that's OK!
 
Slowly add the dry ingredients and the milk to the mix in the stand mixer - alternating ingredients. I scooped in 3 wooden spoon fulls of dry ingredients, let it mix in a bit, then poured in some milk. Then dry, then milk, dry, milk, etc. End with the milk.
 
Scoop out 1 1/2 cups of batter into 6 different bowls. 1 1/2 cups per bowl worked out well for me - though I did not measure carefully. I made a bit of a mess... lol. But I didn't know what the right measurement would be - I was guessing. You can now learn from my trial & error ;-)  I scooped batter out with a measuring cup... I don't recommend that method - it made a mess and it was really hard to control because batter stuck to the sides of the cup. If I were to do it again, I'd POUR 1 1/2 cups of batter into a measuring cup from the original mixer bowl. I'd scrape out the measuring cup well between bowls to ensure each bowl got 1 1/2 cups. Whisk Kid recommends you do all this using a kitchen scale, by weight... umm... I don't have one of those. If you do, you're life jsut got easier when it comes to making this cake, just follow her guidelines for dividing the batter up.
 
Now add food coloring to each bowl. You could do all shades of pink & red if you're making it for a little princess. Do the rainbow I made (notice I layered my colors differently than Whisk Kid - I liked it better this way). Do all pastels for Easter. Or do anything you want with the colors.
 
I greased 9'' round cake pans liberally with crisco. Then lightly floured them. I don't have parchment paper - Whisk Kid recommends you use that... but my method worked fine - 100% no-sticking :)  And I have cheap, dollar-store round cake pans! I only have 3, so I did this in two shifts.
 
Pour one bowl of batter into the 9'' round pan. It will not fill it. Take the back of a knife or spoon and swoosh it around so it appears level and takes up the whole pan.
 
Then bake the cakes at 350 for 15 minutes. My oven tend to run a little hot - and 15 minutes was practically perfect. So you may need more time. You want them done so that a toothpick comes out clean when you stick it in the center. And the cake should have a little spring to it when you touch it with your fingers.
 
Let the cakes cool on a wire rack, and/or in the fridge. These cakes were amazingly durable - they didn't fall apart easy and were easy to work with and move around a lot - I only have 2 wire racks... and only so much room in that fridge!
 
Once cool, you'll need to level your cakes. Notice how they all have a hump in the middle from baking?? If you stack them now, your cake will have a giant hump in the middle and probably won't be level or straight. I used a long serraded bread knife. But I think I'm going to invest in one of these bad boys...





They're only like $4 - and will do a much better job at leveling a cake! 

Once all cakes are level, it's time to stack! Lay the first one down on you're serving platter. If you have a turn table, use that! If you don't want to start right on your serving platter, put the cake on one of those cardboard cake round things you can get for cheap at places like Michaels or Hobby Lobby. That will make it easier to move to another serving dish later.

And another tip, slip wax paper under the edges of the bottom layer - just tuck it under the edge. This way, when you spill icing (if you're like me, you will!), you don't have to worry. You can slip the paper out when you're done and have a clean surface - no one will know the mess you made!

Icing... I didn't use Whisk Kid's recipe. Not because I don't like to make homemade icing, I just didn't feel like it ;-)  I bought four cans of Duncan Hines icing instead. Two vanilla and two rainbow chip. I spread rainbow chip between the layers - I used about 1 1/2 cans for just this. Next time, I think I'll use regular vanilla icing for in between the layers instead. And ice the side of the cake in rainbow chip ;-)

After all the layers are stacked, I dirty iced it. That is, I spread a very thin coat of vanilla icing all over the cake. I used it to fill in the gaps between the layers, too. Then I let it sit in the fridge for a half hour. Why? Because that let the icing harden. So when I went back to ice the cake for real, I didn't have to worry about mulit colored cake crumbs mixing in with my white icing. That way no one could tell what laid beneath that pretty white icing!

After I iced the cake, I removed the wax paper strips and TA DA! Almost done :)  I took some tips from my friend, Lauren - who taught us some techniques in cake decorating at a previous MOPS meeting. She said cakes look more professional if you pipe a line of icing along the bottom of the cake - where it touches the serving dish. And another piped line around the top outside edge. So, I took my remaining vanilla ising (about 1/3 a can) and mixed in some red & blue food coloring, to make purple. And I piped it along those edges. Sure enough - it looked so much better! I used the star tip and it could not have been easier.

Then I stuck some of those store-bought candy letters on the top and VIOLA! All done. And ready to impress unsuspecting cake eaters who think it's a boring old, normal cake inside ;-)

How's it taste? Pretty darn good if I do say so myself! It's very moist and yummy. But I'll warn you, if you don't like icing, this probably isn't the cake for you. Cause there's a lot of icing! It's sweet alright. But in a very good way (in this cake-lover's opinion)!