Rainbow Heart Sprinkle Cake with a surprise inside!

Rainbow Heart Cake

There are some cakes that just speak to me. I have an entire folder of favorite cakes that I save in hopes that someday I can use them for inspiration. This month I had a request for a rainbow themed birthday cake. I must say, I was over the moon because I have saved up several cheery rainbow themed cakes. Probably my favorite is this rainbow heart cake  by Wild Orchard Baking Company that I discovered on Half Baked. rainbow_heart_cake_1My second favorite is the new trend of covering the entire cake in rainbow sprinkles. Sprinkles just bring out my inner 5 year old. I was torn between these two styles of cake and so was Molly’s mom.  On a whim, I thought why not make them both in one rainbow, heart, sprinkle cake.
Time for the nitty gritty. How did she do that:

Cake Details:
6 inch chocolate cake(bday girl’s favorite)  top tier
10 inch rainbow vanilla cake  bottom tier


6 and 10 inch cake boards
Supports of choice for tiered cake – I use the Single Plate System(SPS) by Bakery Craft
12″ Round Cake Drum
Rainbow food colors – Christmas red,orange, lemon yellow, leaf green, sky blue, violet, pink
Fondant – 5-6 ounces of each color is enough for the hearts, balls and name
Sprinkles – 6 ounces of multi-colored nonpareils (fancy word for round sprinkles)
 2.5 batches of white buttercream (a single batch is based on 2lb of powered sugfar)
Letter Cutters- FMM Funky Tappits and FMM Script Tappits were used for Molly’s name
Small heart cookie cutter
Large heart template – I created this template on a Cricut to cut out a  4 1/2 inch George(cartridge) heart.
#12 Wilton piping tip and a piping bag
Small offset spatula
Wax paper
Cooking spray

 Heart Tier Instructions:
heart tierThe number of hearts needed will be dependent on the size of heart cutter you use. I lucked out and happened to have a heart cutter that fit exactly 14 (2 sets) of the rainbow hearts on each row. Officially a rainbow has 7 colors (red, orange, yellow, green, blue, indigo, violet.) I replaced indigo with pink for a little extra variety.  
Use a couple of pieces of paper and outline your hearts to figure out how many will fit. I even labeled them with colors to help me test how many of each color I would be using. For a 6 inch cake, you need to cover a rectangle that is approximately 4in(height of the cake) X 20 inches(circumfrance of a frosted 6 inch cake).

For my cake, I needed a total of 42 hearts (6 of each color).   Roll out each color of fondant to 1/16 inches thick. Cut your hearts and keep them in a ziplock bag so they stay soft. You can do this a couple of days in advance as long you keep them sealed. I made 1 extra of each color just in case.

Fill and frost your 6 inch cake. Starting at the front of the cake place the first 3 hearts vertically. If your frosting has crusted, apply a small amount of buttercream to the back of the hearts before you apply them. Add the next column of hearts to the left, then add the column to the right. Continue adding hearts left and right of the center. This makes sure any “adjustments” you need to make will be in the back. When I was 2/3 of the way done, I recalculated my spacing between hearts to ensure they would all fit nicely on the cake.

Sprinkle Tier Instructions:
rainbow cake insideFor this tier, I wanted to carry the rainbow from the outside into cake.  I baked individual layers to create the internal rainbow effect. I used only 6 of the 7 colors of the rainbow for the inside. I didn’t want the top tier to be super tall. I used just under two batch of vanilla cake. You want the tiers the same size, so you want to weigh or meause the amount of batter you make of each color. For the 10 inch cake, I used 2.25 cups of batter for each layer. I separated the batter and used the same gel colors I used for the hearts to color the batter. To make sure the color would stay bright, I added enough food coloring to achieve the color I wanted then added an extra dab. Bake each layer at 300 to 325 degrees. You want to bake these thinner layers at a lower temp so that they do not dry out and they do not dome. I did not have to level these thin layers.  Once cooled, wrap each layer to keep them moist while the other layers bake.  Freezing the layers for 15-20  minutes will make it easier to stack them later on.rainbow cake before icing
Place a smear of buttercream on the 10 inch cake board and place the purple tier onto the board.  Load your buttercream into a piping bag with a #12 tip. Pipe a layer of frosting over the entire layer and smooth it with a spatula. Add the next layer of cake, repeat layer of frosting until you complete your cake rainbow. Then frost the outside of the tier using your normal method. Smooth the front portion of the well where the white heart and name will go.

Applying the Sprinkles:
Before I applied the sprinkles, I took my large heart template and placed it on the cake. If you let your buttercream crust up a little you can attach your template with a little shortening around the edges.  There numerous suggestions on how to apply sprinkles. So people say to use your hand and kind of press them into the cake. I tried that first and made a massive mess in just one handful so that was a total failure. Half Baked did a blog post where she chilled her cake and rolled the edges in sprinkles which would work great for a small cake or cupcakes but there is no way I could do that with a 10 inch tier. When researching sprinkle cakes, I came across a post on how to apply sprinkles to the side of a cake and since I was out of options, I thought I would give it a try and to my total amazement, it WORKED! Cut a strip of wax paper. I did best with strips around 2X 4 inches and place it on a deep cookie sheet or baking pan.  Spray lightly with cooking spray. Literally sprinkle the sprinkles onto the sprayed wax paper. Shake it around a bit so the sprinkles form a single layer. Lift the wax paper and gently place it onto the side of the cake. Lightly rub your hand over the wax paper to transfer the sprinkles from the wax paper to the cake. Lift the wax paper off. if there are any sprinklesbottom tier still on the wax paper, just move it to a bare spot on the cake and rub light over that spot. Do not press too hard or the buttercream squishes out between the sprinkles. Repeat until the cake is covered. I’m not saying you won’t have sprinkles bouncing around your counter but it is much cleaner and easier to do than trying to press them into the side. Don’t forget to pay special attention to the area around the heart template so that you get a very well defned sprinkle outline around the heart.  Gently remove the template.

Cut out your letters in the rainbow colors. I used the Funky Tappits for the M and the Script Tappits for the rest of the letters. Roll out a fondant snake and create the swirl accents. Leave these items to dry. Roll out the fondant balls for the border. I made 8 fondant balls of each color and had a few extras. Attach the letters with buttercream and attach the fondant balls to the cake drum with melted chocolate. Don’t forget to add a ribbon to your cake drum and you are all set for a whimsical rainbow, heart, sprinkle cake.

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  1. Wonderful, thanks so much for sharing!

  2. what size of heart cutter did you use? thanks for the tutorial!

    • Hi Pam, I just went and measured the cutter. It measures at it’s widest point just under 1 1/2 inches. I hope that helps.

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