Happy St. Patrick’s Day! And happy birthday to my sweet niece Maren who is having a great 2nd birthday party in Brooklyn today that we are sadly not attending. My parents will be there to help celebrate the big day with my sister’s family. Happy Birthday, Maren!
We don’t really do St. Patrick’s Day, but I was seeing so many fun rainbow and pot o’ gold crafts, snacks and baked goods on blogs and on Pinterest that I just had to make this rainbow cake. I’d originally seen rainbow cakes in layers, which I think is so beautiful and orderly. But I do not have enough cake pans of the same size, nor do I have the patience and willingness to make 3 cakes, then wash and dry the pans and make 3 more. So I found this rainbow cake on Hostess with the Mostess who links to Omnomicon’s tutorial for making this fun and easy rainbow cake that only requires you to have 2 cake pans of the same size! Perfect.
I used the cake recipe from Omnomicon, which is simply 2 white cake mixes and 3 cups of Diet Sprite. No oil, no eggs, no joke. So I suppose this cake could be considered “good” for you. But then I used a not so good for you buttercream instead of the cool whip and pudding frosting that she uses. The cake in its entirety is kind of like ordering a diet coke along side your big greasy hamburger.
The cake recipe honestly had me a little worried. Was this diet soda thing really going to work? Well, it did! For the most part anyway. The cake took a little longer to bake, about 40 minutes, and even then it was so moist that it fell apart a little after being removed from the pans. One layer split almost totally in half, but I was able to squish it back together with the help of a bit of frosting. It was also stickier than normal cake mix cakes. I let the cakes cool upside down on racks and when I went to take them off I had more breakage because it had stuck to the rack. Again, frosting repair was needed. Here is but one of my frosting repair jobs.
But even with the problems that made cake assembly a little difficult it was oh so very tasty, moist and delicious. I think with cupcakes you could use this cake mix + diet soda method and be quite pleased with the results since you don’t have any layering to do, and there’s less guilt involved. I think you might only get 12-18 cupcakes out of one cake mix and 1 1/2 cups of diet soda. 2 cake mixes and 3 cups gave me what a cake mix with the usual eggs and oil would have. But there might be some deflation due to mixing the batter once all together and then again to make the colors. I don’t know. I am not a scientist.
Dividing and coloring the cake batter was pretty simple. I used a scale to get the same amount in each of my 6 bowls, but you could easily eyeball it and not suffer any serious consequences if you were a little off. You really should use gel colors if you want the lovely bright colors. The food coloring you use for dyeing Easter eggs won’t cut it. I used Wilton gel colors. If you do any cake or cookie decorating at all, you should have some of these.
Grease and flour 2 8-inch cake pans and fill the first pan with red, orange and yellow. Pour the red in first, right in the center of the pan. Follow with the orange, also right in the center and try your best to make it a circular shape (mine was kind of amoeba shaped) and the do the same with the yellow. In the second pan fill with green, blue and violet. If you are a science nerd you noticed that I left out Indigo from ROYGBIV. Feel free to divide your batter into 7 and make yourself some indigo colored batter, but I took a short cut and liked the ease and equality of 3 colors in each pan.
Use your favorite recipe for vanilla frosting or the one below. I love the white frosting against the bright colors of the cake. This cake is a lot of fun. It would be great for a kid’s (or adult’s) birthday party. You can use the same method with cupcakes, just layer the colors with teaspoons of batter. In a 9×13 pan it might be hard to get good layers, so you could just randomly dollop colors for more of a tie-dyed effect. If you do bake in something other than 8-inch cake pans, refer to the baking times and temps on the box of cake mix and then check for doneness, adding more time if needed.
- 2 boxes white cake mix
- 3 cups (24 ounces) diet lemon-lime soda
- Preheat oven to 350°F.
- Mix cake mixes and soda together until well combined.
- Divide batter evenly into six bowls.
- Color each bowl of batter red, orange, yellow, green, blue and violet.
- Grease and flour 2 8-inch cake pans. Pour red, orange and yellow batter into one cake pan, starting with red, yellow on top of that, and then orange. Repeat with green, blue and violet.
- Bake for 35-40 minutes or until tops bounce back when pressed lightly or cake tester inserted into the the center comes out clean.
- Let cool in pans for 10-15 minutes then remove and let cool completely on racks.
- Level cakes if desired, then layer one cake on a plate or cake stand. Frost with vanilla icing, top with second layer of cake and put on a crumb coat of icing. Refrigerate for at least 1 hour.
- Finish frosting the cake with the remaining icing, chill until ready to serve.
Simple Vanilla Buttercream
- 3 sticks of butter, softened
- 4 1/2 to 6 cups of powdered sugar
- 2 teaspoons vanilla extract
- 2-4 tablespoons milk or cream
- Beat butter until smooth, then add in powdered sugar. Start with 4 1/2 cups, then add more in 1/2 cup increments to achieve a thick but still spreadable consistency.
- Beat in vanilla and milk, starting with 2 tablespoons and adding more if needed.
- Use to generously frost a layer cake or 24 cupcakes.