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Rainbow Surprise-Inside Cake

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Betty Crocker Kitchens
Updated May 19, 2026
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Prepare to amaze your guests with a dessert that's more than meets the eye! Introducing Betty Crocker's spectacular Rainbow Surprise-Inside Cake. From its elegantly simple exterior, no one will guess the explosion of color and fun waiting within. Slice into this incredible cake to reveal a cascade of vibrant candies, creating a truly unforgettable moment for any gathering. Whether it's a birthday, holiday, or just a fun weekend treat, this recipe promises smiles and gasps of delight. It's surprisingly easy to create this show-stopping centerpiece that brings joy to all ages. 

Recipe Ingredients

From the essential Betty Crocker cake mix to the colorful M&M's that make the "surprise" so special, we've got everything you need listed below. 

Betty Crocker™ Delights Super Moist™ Party Rainbow Chip Cake Mix: The perfect foundation for an easy rainbow cake recipe.

Betty Crocker™ Whipped Vanilla Frosting: Creates a smooth, classic finish for your surprise-inside cake.

M&M's® Candy-Coated Milk Chocolate Candies: Essential for the vibrant M&M cake filling.

M&M's® Minis Candy-Coated Milk Chocolate Candies: Adds extra color and texture to the fun cake surprise.

Confetti Sprinkles: For a festive garnish on this colorful dessert.

Other Ingredients You’ll Need: Water, vegetable oil, and eggs

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How to Make Rainbow Surprise-Inside Cake

Creating this delightful cake is so simple, even a novice baker can achieve a spectacular result.

1. Make the Cakes

Make and bake as directed on the box for 8-inch round cake pans. Be sure to cool the cake pans completely, then wash, dry, and spray with cooking spray before baking the second cake mix. You will be baking 4 rounds total.

2. Create Your Layers

Once the four cake layers are cool, use a serrated knife to level their tops. This makes them flat for stacking. Next, take two of these leveled layers. Use a 4-inch round cutter to cut a circle from the center of each. These will be the "walls" for your candy filling. If you don't have a cutter, trace a 4-inch circle on parchment paper, cut it out, and use it as a guide for your knife.

3. Assemble the Layers

Start with an uncut layer. Spread about 1/3 cup of frosting evenly over the top. Carefully place one of the cake layers with the center removed on top, aligning it precisely. Spread more frosting, then add the second center-removed layer, followed by frosting, building the structure that will hold your exciting surprise!

4. Fill and Frost

Combine your M&M's® candies, M&M's® minis, and confetti sprinkles for a vibrant, even mix (about a 1/2 cup).  Pour the mixture into the center of your cake and gently press down to flatten. Place the final uncut layer on top. Generously frost the outside of the cake and consider using additional M&M's® or sprinkles for decoration. 

How to Store Rainbow Surprise-Inside Cake

Keep the cake loosely covered with tented plastic wrap or in a cake dome. Store at room temperature for up to 3 days.

Rainbow Surprise-Inside Cake

  • Prep Time 30 min
  • Total 3 hr 25 min
  • Servings 16
  • Ingredients 6
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Ingredients

  • 2 boxes Betty Crocker™ Delights Super Moist™ Party Rainbow Chip Cake Mix
  • Water, vegetable oil, and eggs called for on cake mix boxes
  • 2 tubs (12 oz) Betty Crocker™ Whipped Vanilla Frosting
  • 2 cups M&M's® candy-coated milk chocolate candies
  • 1 cup M&M's® minis candy-coated milk chocolate candies
  • 3/4 cup from 1 container Betty Crocker™ Parlor Perfect Ice Cream Topping Confetti Sprinkles

Instructions

  • Step 
    1

    Heat oven to 350°F (325°F for dark or nonstick pans). Spray the bottom and sides of two 8-inch round cake pans; line with parchment paper.

  • Step 
    2

    In a large bowl, beat 1 box of cake mix and the ingredients called for on the box with an electric mixer on medium speed for 2 minutes, scraping the bowl occasionally. Divide batter between pans. Bake as directed on the box for 8-inch round cake pans. Cool 10 minutes. Remove from the pans to a cooling rack; remove parchment paper. Cool completely, about 1 hour. Meanwhile, repeat mixing and baking with the second box of cake mix to make 2 more layers.

  • Step 
    3

    Level the cake layers by trimming off the rounded tops. In 2 of the layers, cut a circle out of the center, using a 4-inch round cutter.

  • Step 
    4

    Place 1 uncut cake layer on a cake stand or serving platter; spread 1/3 cup frosting on top. Top with 1 layer of cake with center removed; spread 1/3 cup frosting on top. Top with the second layer with the center removed; spread 1/3 cup frosting on top.

  • Step 
    5

    In a small bowl, mix chocolate candies and sprinkles. 

  • Step 
    6

    Fill the cake with the chocolate candies and sprinkles. Gently press candies to level. 

  • Step 
    7

    Top with the final uncut cake layer. Frost the side and top of cake with remaining frosting.  

Nutrition

630 Calories
32g Total Fat
5g Protein
80g Total Carbohydrate
63g Sugars

Nutrition Facts

Serving Size: 1 Serving
Calories
630
Calories from Fat
290
Total Fat
32g
50%
Saturated Fat
14g
72%
Trans Fat
0g
Cholesterol
75mg
25%
Sodium
280mg
12%
Potassium
125mg
4%
Total Carbohydrate
80g
27%
Dietary Fiber
1g
4%
Sugars
63g
Protein
5g
% Daily Value*:
Vitamin A
4%
4%
Vitamin C
0%
0%
Calcium
10%
10%
Iron
6%
6%
Exchanges:
1 Starch; 0 Fruit; 4 1/2 Other Carbohydrate; 0 Skim Milk; 0 Low-Fat Milk; 0 Milk; 0 Vegetable; 0 Very Lean Meat; 0 Lean Meat; 0 High-Fat Meat; 6 1/2 Fat;
Carbohydrate Choice
5
*Percent Daily Values are based on a 2,000 calorie diet.

Recipe Tips

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