Rainbow cakes have been all the rage on Pinterest for some time now, and I love making rainbow treats, particularly around St. Patrick's Day. This year, I wanted to incorporate the rainbow theme with a chocolate cake because, in my book, everything is better with a little chocolate. But that meant I couldn't just dye the cake layers. I had to get a little creative. So my answer to the challenge of a Chocolate Rainbow Cake is this beauty.

🥘Ingredients:

• For the Cakes:
• all-purpose flour
• cocoa powder
• baking soda
• salt
• granulated sugar
• vegetable oil (I used coconut oil, melted and cooled)
• egg
• milk (whole or 2%)
• vinegar
• For the Frosting:
• unsalted butter, softened
• confectioners' sugar
• vanilla extract
• whole milk
• For Decorating:
• Food coloring - I used AmeriColor Food Gels in the following colors:
• Tulip Red
• Orange
• Lemon Yellow
• Leaf Green (with a drop of Electric Green)
• Royal Blue
• Violet (with a drop of Electric Purple)

🔪How to make a Chocolate Rainbow Cake?

This Chocolate Rainbow Cake is incredibly easy to make. Instead of incorporating the rainbow into the chocolate cake itself, I used the frosting, particularly the frosting between the layers, to provide the rainbow effect.

I used a 6-inch round cake pan to make all three layers. After baking, cooling, and leveling the cakes, I whipped up a batch of vanilla frosting.

I divided the frosting into six containers, and I tinted each portion with a color of the rainbow. Using a piping bag fitted with a large tip (I used a #10 tip) for each color, I frosted the cake like this:

After filling the second layer in the same manner, I put the cake in the fridge for about 20 minutes to let it set. Then I put a thing layer of frosting all over the cake to seal in the crumbs. Threw it back in the fridge for about 30 minutes.

Finally, I put on the final layer of frosting and the decorations.

What makes this Chocolate Rainbow Cake so amazing?

While the outside of this Chocolate Rainbow Cake is festive and rainbow in it's own right, it's the inside of the cake that's the real showstopper. When I cut into the cake, my kids were blown away with the rainbow filling.

My older daughter asked me, "How did you paint a rainbow on the inside of the cake?" And another guest exclaimed, "Oh, I thought it was just the outside of the cake that was rainbow. I couldn't image how the inside of a chocolate cake could be rainbow!"

And there you have it. Mission accomplished - a Chocolate Rainbow Cake!

If you love rainbow foods as much as I do, or you're looking for some good old St. Patty's Day inspiration, check out these St. Patrick's Day Cookies and these St. Patrick's Day Crafts for Kids.

If you are looking for more fun and festive cake recipes, do check out this recipe for Gingerbread Bundt Cake and Halloween Bundt Cake.

Chocolate Rainbow Cake Recipe

This moist, rich Chocolate Rainbow Cake is perfect for St. Patrick's Day! While the outside of the cake is festive, it's the inside of the cake that has a bright, rainbow filling.

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Course: Dessert

Cuisine: American

Prep Time: 1 hour hour 30 minutes minutes

Cook Time: 30 minutes minutes

Total Time: 2 hours hours

Servings: 6 people

Calories: 1101kcal

Ingredients

For the Cakes:

• 1 ¼ cups all-purose flour
• ½ cup cocoa powder
• ¾ tsp baking soda
• ¼ tsp salt
• 1 cup granulated sugar
• ⅓ cup vegetable oil I used coconut oil, melted and cooled
• 1 large egg
• ¾ cup milk whole or 2%
• 1 tbs vinegar

For the Frosting:

• 2 cups unsalted butter softened
• 5 cups confectioners' sugar
• 2 tsp vanilla extract
• 1 to 1 ½ tsp whole milk

For Decorating:

• Food coloring - I used AmeriColor Food Gels in the following colors:
• Tulip Red
• Orange
• Lemon Yellow
• Leaf Green with a drop of Electric Green
• Royal Blue
• Violet with a drop of Electric Purple

Instructions

For the Cake:

• Preheat the oven to 350 degrees F.
• With parchment paper, line 3 6-inch round pans. Grease the pans. Set them aside.
• In a medium bowl, sift together flour, cocoa powder, baking soda, and salt.
• In a large bowl, whisk the sugar and oil together.
• Add the egg and vanilla and whisk until just combined.
• In a measuring cup, add the milk and vinegar.
• In three additions, alternately add the dry ingredients and the milk to the sugar mixture. Start and end with the dry ingredients.
• Mix until just combined.
• Divide the batter evenly between each of the pans.
• Bake for about 30 min or until a toothpick inserted in the center of the cake comes out clean.
• Allow the cakes to cool in the pans for about 15 min. Then invert on to cooling racks. Allow the cakes to cool completely.

For the frosting:

• In the bowl of a mixer fitted with a paddle attachment, mix the butter and sugar until fluffy.
• Add the vanilla and cream. Beat until fluffy.
• Measure out a scant ¼ of a cup of frosting in 6 separate bowls. Tint each bowl with one color of the rainbow.
• Place the frosting in pastry bags fitted with large tips. (I used #10 tips)
• Level the cakes.
• Then fill them as shown in the photo in the post.
• Once the cakes are filled, place the cake in the refrigerator to chill for about 20 minutes.
• Use the remaining frosting to crumb coat and frost the cake.
• The leftover colored frosting can be used to decorate the cake.

Nutrition

Calories: 1101kcal | Carbohydrates: 139g | Protein: 3g | Fat: 63g | Saturated Fat: 40g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 16g | Trans Fat: 2g | Cholesterol: 166mg | Sodium: 260mg | Potassium: 174mg | Fiber: 2g | Sugar: 133g | Vitamin A: 1942IU | Calcium: 65mg | Iron: 1mg

If you're interested in checking out all of my recipes, you can find me at The Crafting Foodie where I share decadent desserts and healthy, easy to prepare weekday meals.