Gluten Free Rainbow Lego Cake

by - October 10, 2018

If you follow my blog you know that I love to make my kid's birthday cakes.  I have been pretty open to what I might be able to accomplish and my kids are set on testing my skills.  My son turned 8 back in June and he wanted to have a bowling party complete with a bowling ball cake.  My middle son turned 6 a couple weeks ago and we celebrated at Legoland so of course he wanted to have a Lego cake.  I did my research to see how I would be able to make this cake.  We invited family over to have cake and ice cream and we have a lot of family so I needed a really big cake.  I thought it would be the best to use two cake mixes to get a big enough cake to make for the whole family.  While I was thinking about how best to do this, I thought making a rainbow cake would be super fun so I needed to factor that into figuring out how this birthday cake would work.

I tried to find someone that had made a rainbow Lego cake and I couldn't find anything.  I found different ways to make a Lego cake but nothing matched what I had in my head so I just had to go for it.  Most people that made a Lego cake baked the cake in a regular cake pan and then cut the cake into the desired shape.  Since I wanted to make a rainbow cake, that method wouldn't really work. I kept thinking about using a loaf pan but I couldn't find anyone that had used one so I wasn't sure if it was a good idea.  I kept thinking about it for a few days but couldn't really come up with a better way than using a loaf pan.  I knew that each layer would be the same size and a rectangle the exact size that I was looking for so I just went with it.
I knew it was important to have each of the layers the exact same size but I don't have a scale so I had to figure out another way to do it.  I decided to use 1 cup of batter for each layer and it ended up being perfect.  I had the exact amount of batter to use for each layer and they came out perfect.  The only thing that was super annoying with making this cake was that I only had one loaf pan so I had to bake each layer individually so it ended up taking forever.  I would also recommend that you use enough food coloring to make the colors really vibrant.  If you are going to go for a rainbow cake, you really want those colors to pop.  With all these layers, it ended up being pretty tall and I was afraid it was going to fall over so I found some straws and stuck them in so it would give the cake some support and wouldn't fall over.  Glad I did so I didn't have to worry about it all night and it was fully supported even when I cut into it so I highly recommend doing that.
The next thing that I had to figure out was how to frost it.  I had made my own fondant when I made the bowling ball cake and I knew that I didn't want to add that step to this cake so I decided to buy it.  You have to really check and read labels to find gluten free fondant because some store bought fondant contains wheat and you really don't want to use those.  I found some gluten free blue fondant so i decided to make it a little easier for myself  and just buy it instead of making it. I wanted a uniform look over the whole cake and fondant seemed the best way to get that look but you could definitely skip that step and just use dyed buttercream.  It is completely up to you.
After I figured out the frosting I had to figure out the knobs on top to make it look like a Lego.  I found lots of different ways to make them but I thought that the best way to make them would be to use gluten free chocolate sandwich cookies.  I used the leftover fondant and covered the cookies in it and they turned out perfect.  It was so easy to make and it turned out to be the easiest part.  All in all, I was pretty happy with how this cake turned out.  It definitely wasn't perfect but my son loved it and it tasted amazing and that is really all that matters.  He loved the colors as well as the Lego shape and it just being the perfect cake for a Lego themed birthday.  It really wasn't as hard as it looks and it definitely doable.  You can always cut the recipe in half to make a smaller cake or not do a rainbow cake to make it easier.  It was really fun to make and I was really proud.  Make sure to check out the video down below to see exactly how I made it and head over to my YouTube channel for more great recipes and product reviews.
Yield: 20 servings

Gluten Free Rainbow Lego Cake

A fun and delicious gluten free cake that is perfect for any birthday or fun party!
prep time: 1 hourcook time: 1 hour and 12 minstotal time: 2 hours and 12 mins


Rainbow Cake
  • 2 (15 ounce) yellow gluten free cake mixes
  • 1/2 cup vanilla instant pudding mix
  • 1 1/2 cups milk
  • 2 sticks unsalted butter, softened
  • 6 large eggs
  • 2 tablespoons pure vanilla extract
Vanilla Buttercream Frosting
  • 2 sticks unsalted butter, softened
  • 7 cups powdered sugar, sifted
  • 6 tablespoons milk, or more as needed
  • 1 tablespoon pure vanilla extract
  • gluten free food color in red, orange, yellow, green, blue and purple
  • gluten free colored fondant, optional
  • 6 gluten free chocolate sandwich cookies
  • 6 straws or wooden dowels for support


Make the Cake
  1. Place rack in the center of the oven and preheat oven to 350 degrees F.  Lightly mist a 9x5 inch loaf pan and dust with gluten free flour. Shake out the excess of flour and set pan aside.
  2. Place cake mix, pudding mix, milk, butter, eggs,  and vanilla in a large mixing bowl and beat with an electric mixer or stand mixer on low speed until the ingredients are just incorporated, 30 seconds. Stop the machine and scrape down the side of the bowl with a rubber spatula. Increase the mixer speed to medium and beat the batter until smooth, 1 to 1 1/2 minutes longer. The batter should look well blended. 
  3. Add 1 cup of batter to a large mixing bowl and add enough red food coloring to get the desired color. Mix until well combined. Poor batter into prepared loaf pan and bake for about 12 minutes or until the top springs back when lightly presses. Transfer loaf pan to wire rack and let cool for 5 minutes. Run a sharp knife around the edge of pan and then flip the cake out onto a wire rack to cool completely.  
  4. Repeat the above step with the colors orange, yellow, green, blue, and purple until all six layers of cake are baked and cooled. Wrap each layer in plastic wrap and chill for 30 minutes before frosting.
Make Vanilla Buttercream
  1. Place the butter in a large-size mixing bowl and beat and beat with an electric mixer or stand mixer on low speed until fluffy, about 30 seconds. Stop the machine and scrape down the sides of the bowl before adding the sifted powdered sugar. Add half of the powdered sugar and mix until full incorporated before adding the other half. Add milk and vanilla and beat about 1 minute until frosting is light and fluffy. Beat in up to 1 tablespoon more milk if the frosting seems to stiff. 
Assemble the Cake
  1. Transfer the purple  layer, right side up to a serving plate. Spread the top with about 1/3 cup frosting before putting on the blue layer. Continue to frost each layer in the order of purple, blue, green, yellow, orange, and the red would be the final layer. After placing all the layers insert straws or wooden dowels straight down into the cake to give the cake support. Cut the remaining straw  off at the top and continue to frost the top and the side of the cake until the cake is covered.  Place cake in refrigerator while rolling out the fondant.
  2. Roll out fondant according to the package directions. Transfer rolled out fondant onto the cake and carefully smooth down over the frosted cake, making sure to cover all the sides.  Cut off the excess fondant and set aside.
  3. Roll out excess fondant into a thin layer. Wrap fondant over the gluten free chocolate sandwich cookies and place on the cake.  You might need to get a tiny piece of fondant and get it wet and put it on the bottom of the cookie to attach it to the cake. 
  4. After cookies are placed, cake is finished.  You can decorate it however you would like or just add some birthday candles for the best birthday cake ever. Slice and enjoy!
Created using The Recipes Generator

You May Also Like