A super awesome rainbow heart hidden inside of a chocolate bundt cake, what could be more fun? This easy rainbow cake is made using boxed cake mixes, which just cuts down on the effort, without sacrificing the WOW factor.

I don't recall what I was originally searching for online one day but I came across the BBC Good Food's Recipe for a Hidden Heart Cake and inspiration hit. I instantly thought to myself that I needed to try it. But, the more I thought about it the more inspired I became to make my own hidden design cake.
With it being June, pride month gear and celebrations are everywhere so this cake could easily fit in with fun gatherings. Who wouldn't love a pride cake at graduation or a BBQ?
On the other hand, with girls and rainbow lovers like my daughter, this cake is simply a fun one to make and can be for anything from a simple surprise dessert to a birthday cake.
Speaking of birthday cakes, this hidden heart cake recipe was sooooo much faster and easier than making the 6 layer vegan rainbow cake I made for my daughter's 7th birthday!
🥘 Ingredients
- Yellow Cake Mix
- Devil Food Cake Chocolate Cake Mix
- Eggs
- Oil
- Water
- Food Coloring
- Cocoa Powder
🍽 Equipment Needed
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- Bundt Pan
- Heart Shaped Cookie Cutter
- 6 Ziploc Bags
- Baking Sheet
- Parchment Paper
🍴 Recipe Tips
This heart cake recipe is pretty simple and easy but there are a few tricky things to note when making your cake with heart inside. You want the cookie cutter to fit inside of the pan with room to spare. I didn't know what size heart cookie cutters I needed so I bought an assorted size pack to make sure my bases were covered.
If you want the heart to pop more when sliced into, try and get the red and lighter colors of the rainbow on the outer sides of the heart with purple stripped down the middle. This will help it to look less hidden once sliced. In person it's much more vivid than in photos.
Freezing the hearts after cutting them makes them easier to handle and place. I do not recommend skipping this step as the hearts can break and make life a bit difficult.
Stack your hearts in 3 or 4 of height at a time and place them in, too many at once will cause straight lines and uneven heart circle whereas too few will allow more chances for the chocolate batter to get between the hearts.
💭 FAQs
If you slice this cake and find a little chocolate covering the heart and ruining the perfect image you had in mind I have a great tip. Simply shave off a small piece of cake. A very thin layer right off of the side of that one you just cut is all you should need.
This cake lasts as long as a normal boxed cake mix should. About 3-5 days at room temperature before getting dry and sad.
Nope! I had None of my stripes matched up to the piece in front of it. You can't even tell! The pieces all fuse together when baked so as you slice it comes out looking awesome. It is a little more noticeable when you do vertical and horizontal stripes side by side but it looks like tie-dye spots, not lines.
🔪 Instructions
Check out how to make hidden heart cake with these simple step-by-step instructions:
- Prepare your yellow cake mix as per the box instructions.
- Preheat your oven to 350F degrees and line a baking sheet with parchment paper.
- Divide the batter into 6 bags and add a drop or more of food coloring into each bag.
- Mix the bags around until the batter is all colored and no stripes of plain batter remain.
- Snip a corner off of the bags.
- starting with red and working your way to purple, slowly pipe stripes of color on the baking sheet until it's filled in. Make sure to keep the stripes thinner so you can fit them all in a heart.
- Bake in the oven for 10-15 minutes until cooked through.
- Let cool for 10 minutes before cutting into hearts (they're less likely to break this way).
- Cut out your hearts, trying to get as many out of the pan as you can.
- Freeze the hearts for 10-30 minutes.
- Make the chocolate cake according to the box.
- Grease the inside of your bundt pan and dust it with 1 tablespoon of cocoa powder to keep the cake from sticking.
- Pour in about 1 cup of cake batter (a little more won't hurt) try to get the batter to make a ring around the pan.
- Stack your frozen hearts in 3 or 4 at a time and place them in the pan. Try to avoid as many cracks as you can. Place them bottom points facing up.
- Fill in the bundt pan with the remaining chocolate cake batter, make sure to cover the ends of the hearts that are sticking up.
- Bake in your oven at 350F degrees for 35-40 minutes until cooked through.
- Let cool in the cake pan for 10 minutes before flipping over onto a wire rack and removing from pan.
How to make the chocolate ganache
- Make the chocolate ganache by combining the chocolate chips and heavy cream in a microwave safe bowl.
- Microwave in 30 second bursts, stirring between each until smooth. This should take about a minute.
- Pour the ganache over the cake.
- Allow 10 minutes or more to set and cool completely.
- Cut and serve your cake. Enjoy!
Check out these other great cake recipes!
- Oreo Bundt Cake with Marshmallow Icing
- Blueberry Sour Cream Bundt Cake
- Peanut Butter Cream Cheese Frosting
- Chocolate Chip Loaf Cake
- Honey Bee Cupcakes with Honey Buttercream
- Vegan Pineapple Upside Down Cake
📖 Recipe
Hidden Rainbow Heart Bundt Cake
Equipment
- 6 Ziploc Bags
Ingredients
- 1 box Yellow Cake Mix, Prepared ($1.72)
- 1 box Devils Food Cake Mix, Prepared ($1.72)
- Rainbow Colored Food Coloring ($0.04)
- 1 tablespoon Cocoa Powder ($0.10)
Chocolate Ganache
- 1 cup Semi-Sweet Chocolate Chips ($0.99)
- 2 tablespoon Heavy Cream ($0.12)
Instructions
- Preheat your oven to 350F degrees, line a baking sheet with parchment paper and prepare your yellow cake mix as per the box instructions.
- Divide the batter into 6 bags and add a drop or more of food coloring into each bag. Close the lid and mix the bags around until the color is completely mixed and no yellow batter remains. Snip one corner off of the end on each bag.
- Starting with red and working your way to purple, slowly pipe stripes of color on the baking sheet until it's filled in. Make sure to keep the stripes thinner so you can fit them all in a heart cutter.
- Bake in the oven for 10-15 minutes until cooked through. This depends on thickness that you piped.
- Let cool for 10 minutes before cutting into hearts (they're less likely to break this way).
- Cut out your hearts, trying to get as many out of the pan as you can. Place them on another pan and freeze for 10-30 minutes.
- Make the chocolate cake according to the box.
- Grease the inside of your bundt pan and dust it with 1 tablespoon of cocoa powder to keep the cake from sticking. You could also use flour if desired, but it will leave white streaks on the cake.
- Pour in about 1 cup of cake batter try to get the batter to make a ring around the pan. Add a little more if needed and spread it around with the back of a spoon.
- Stack your frozen hearts in 3 or 4 at a time and place them in the pan. Try to avoid as many cracks as you can. Place them bottom points facing up.
- Fill in the bundt pan with the remaining chocolate cake batter, make sure to cover the ends of the hearts that are sticking up.
- Bake in your oven at 350F degrees for 35-40 minutes until cooked through. It may not take as long as a traditional bundt cake would to bake because the center is technically already cooked.
- Let cool in the cake pan for 10 minutes before flipping over onto a wire rack and removing from pan.
How to make the chocolate ganache
- Make the chocolate ganache by combining the chocolate chips and heavy cream in a microwave safe bowl.
- Microwave in 30 second bursts, stirring between each until smooth. This should take about a minute.
- Pour the ganache over the cake.
- Allow 10 minutes or more to set and cool completely.
- Cut and serve your cake. Enjoy!
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