With St. Patrick’s Day coming up, here’s a fun idea to make with the kids… or for the kids: rainbow cupcakes!

We are making the cutest rainbow cupcakes, but not just any rainbow cupcakes, surprise inside rainbow cupcakes! When you cut these cupcakes in half, you can find a rainbow inside. This is not the first time we have shared a fun surprise shape in a cupcake, we shared these fun Surprise Heart Cupcakes a few years ago and we love this element of surprise!

We are updating this post…the original post was shared so many years ago and it needed an update. The original post had full rainbow cupcakes with paper rainbow toppers, but this one has surprise inside rainbow cupcakes. Either way you choose to go (full rainbow cupcakes or just the little surprise rainbow inside), you can’t go wrong…these are still delicious cupcakes either way! Here’s what the cupcakes look like before they have frosting.

What you need to make rainbow cupcakes:

Cupcake Batter:

2 cups cake flour
1/2 cup butter, room temperature
1/3 cup coconut oil
1 cup sugar
1/2 tsp baking soda
1 tsp baking powder
4 egg whites
2 teaspoons vanilla extract
1 cup buttermilk
5 Wilton Gel Food Coloring colors (red-yellow-green-blue-purple)
Buttercream Frosting
1 cup butter, room temperature
3 cups powdered sugar, sifted
2 teaspoons vanilla extract
1/2 teaspoon fine salt
2 tablespoons whole milk
Cupcake Toppers:
Rainbow Airheads Extreme
Rainbow Sprinkles
Special Tools:
small 5inch bundt pan
cupcake pan
cupcake liners

Make the small rainbow bundt cake (this is for the surprise inside rainbow):

Grease the small bundt pan. Preheat oven to 325.
Add 2 tablespoons of the cake batter into 5 separate small bowls. With toothpicks add the food coloring gel colors to each bowl. (red-yellow-green-blue-purple). Mixing each color in well.
Into the small bundt pan add each color into the pan one at a time starting with red. Spread the color red out the most into the pan trying to get it to go up the sides.. With the addition of each color, let the color below be visible in the pan (don’t cover over it completely). At the top put a thin layer of the white batter.
Bake the small cake for 15 minutes at 325. When finished baking, allow it to cool for a few minutes in the pan then invert it onto a parchment lined plate. To speed up the cooling time, move it to the freezer. Once it is completely cool and firm, cut it into 1/2 inch thick slices.

How to make Cake Flour:

If you don’t have cake flour, you can make it. After measuring out the 2 cups of flour needed for this recipe, remove 2 tablespoons of the flour and add 2 tablespoons cornstarch in the place of the flour. Now sift the flour and corn starch together. Now you have cake flour. So easy!

What kind of Food Coloring to use for Rainbow Cupcakes?

We love Wilton brand Gel colors. They are great for giving bright colors without thinning the batter. Both Michaels and Walmart sell Wilton brand Gel Colors.

Why Surprise Rainbow Cupcakes:

We have made full rainbow cupcakes (see below), and we love the idea of the surprise rainbow inside for a few different reasons: One: surprises are always fun! Two they use less food dyes than fully colored rainbow cupcakes (less red dye 40).

Tips and Tricks:

Sift dry ingredients together. Sifting the dry ingredients together is always a good idea when it comes to baking a cake or cupcakes.
Add the sprinkles over a plastic container or over the sink to catch sprinkles that don’t stick to the frosting. Feel free to add more sprinkles if you like more!
To help make sure to cut the cupcakes in half at just the right place to reveal the rainbow colors inside, make a little line on the bottom of the cupcake liner so you can remember which way the rainbow is inside the cupcake. Once the cupcake is frosted, it’s hard to remember or see which way the rainbow cake is going inside, and this little line helps!

Surprise Inside Rainbow Cupcakes

Rainbow Cupcakes with a surprise rainbow inside.

Author Kami | NoBiggie.net

Ingredients

Cupcake Batter:

2 cups cake flour
1/2 cup butter room temperature
1/3 cup coconut oil
1 cup sugar
1/2 teaspoon baking soda
1 teaspoon baking powder
4 egg whites
2 teaspoons vanilla extract
1 cup buttermilk
5 Wilton gel food coloring colors (red-yellow-green-blue-purple)

Buttercream Frosting:

1 cup butter room temperature
3 cups powdered sugar sifted
2 teaspoons vanilla extract
1/2 teaspoon fine salt
2 tablespoons whole milk

Cupcake Toppers:

1 package Rainbow Airheads Extreme
1 small shaker Rainbow Sprinkles

Instructions

Make the Cake Batter:

In the bowl of your stand mixer beat together the butter, sugar, cake flour, coconut oil, vanilla, salt, baking powder and baking soda.
Add the egg whites, one at a time, beating between each one.
Turn the mixer off and add in the buttermilk. Return the speed to medium and let the batter beat for another minute.

Make the small rainbow bundt cake (for the surprise inside rainbow):

Grease a small (5inch) bundt pan. Preheat oven to 325.
Add 2 tablespoons of the cake batter into 5 separate small bowls. With toothpicks add the food coloring gel colors to each bowl. (red-yellow-green-blue-purple). Mixing each color in well.
Into the small bundt pan add each color into the pan one at a time starting with red. Spread the color red out the most into the pan trying to get it to go up the sides.. With the addition of each color of the rainbow, let the color below be visible in the pan (don’t cover over it completely). At the top put a thin layer of a little white batter.
Bake the small cake for 15 minutes at 325. When finished baking, allow it to cool for a few minutes in the pan then invert it onto a parchment lined plate. To speed up the cooling time, move it to the freezer. Once it is completely cool and firm, cut it into 1/2 inch thick slices.

Bake the Cupcakes:

Preheat the oven to 375.
Line a 12 cup muffin pan with paper liners. Into the bottom of each paper liner, add just a bit of batter, about a teaspoon. Place the little rainbows into the center of the cups, with all rainbows facing the same direction, this helps when you go to cut each one in half to reveal the rainbow, so you can know which direction to cut each one.
Add more of the white cake batter around and over the little rainbow cake piece. Each cup should be about 2/3 full.
Bake the cupcakes for about 15 minutes. To check for doneness, gently press the top to see if it feels dry and no longer wet.

Make the Buttercream Frosting:

In the bowl of a stand mixer, cream the butter until it is light and fluffy about 5 minutes. Add in the vanilla, salt and powdered sugar and beat until combined, about 3 minutes. Finally add in the milk and beat to just combine.

Decorate the Cupcakes:

To start, make sure that all the cupcakes have completely cooled. Working one cupcake at a time, spoon about 2 tablespoons of the buttercream frosting onto the top of the cupcake. Smooth out the frosting to look like a little mound on top.
Gently sprinkle rainbow sprinkles around the sides of the frosting.
With a star tip pipe some of the buttercream onto the top to look like little clouds.
Cut one Rainbow Airheads Extreme in half and add half to the top to look like a rainbow on the top of each cupcake. Enjoy!

Recipe Notes

Notes:
If you don’t have cake flour, you can make it! After measuring out the 2 cups of all purpose flour, remove 2 tablespoons of the flour and in it’s place add 2 tablespoons cornstarch. Sift the flour and corn starch together. Now you have cake flour.

Making This Recipe? Tag us on Instagram: @NoBiggie using the hashtag #NoBiggieRecipes, so we can see what you are making in the kitchen!

Rainbow Cupcake Topper Ideas:

paper rainbow cupcake toppers
Rainbow Airhead Extremes candy (cut in half)
pipe the frosting in cloud shapes
gold wrapped chocolate coins
gold sugar sprinkles
mallow bits for clouds

Make a paper rainbow cupcake topper for the rainbow cupcakes:

If you’d like to make paper rainbow cupcake toppers, here’s how:
Trace around the bottom of a clear glass onto white paper to make a circle.
With markers color in a full circle rainbow. This way you create two rainbows at once. Cut out the full circle and then cut the circle in half to make two rainbow cupcake toppers.
With more white paper draw and cut out simple clouds by hand. Assemble the clouds, rainbows together with glue dots onto toothpicks. Now you’re ready to stick them into your cupcakes. That’s it! So festive and fun for St. Patty’s Day, and a great way to involve the kids!