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Rainbow Cupcake on white background with sprinkles
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5 from 3 votes

Best Ever Rainbow Cupcakes

These Rainbow Cupcakes are the best EVER! Super moist and fluffy with a swirly cloud of vanilla buttercream, these showstopping cupcakes are so joyful and perfect for any occasion!
Prep Time15 mins
Cook Time18 mins
Total Time33 mins
Course: Cakes/Cupcakes, Dessert
Cuisine: American, Dessert
Servings: 12


  • One box white or vanilla cake mix
  • 1 cup water or milk
  • 3 large eggs
  • 1/3 cup vegetable or canola oil
  • One (3.4 oz) box instant vanilla pudding mix just the dry mix, do not prepare the pudding
  • Gel food coloring in rainbow colors
  • 3/4 cup unsalted butter at room temperature
  • 1 tsp vanilla extract
  • 1/4 cup heavy whipping cream or milk
  • 3-4 cups confectioners' sugar
  • Rainbow sprinkles or sour rainbow candy belts for decoration


  • Preheat oven to 350° degrees F. Line 1 muffin tin with 12 paper liners; set aside.
  • In a large bowl, beat the cake mix, water, eggs, oil, and dry pudding mix powder together with a handheld electric mixer on medium speed until smooth and creamy, about 2 minutes. Portion the batter evenly among 6 small bowls. Tint each bowl a different color of the rainbow. For my cupcakes, I used red, orange, yellow, green, blue, and purple. For best results, I like concentrated gel food coloring for this.
  • Spoon a heaping teaspoonful of purple batter into the bottom of a muffin cup. Top with a teaspoon of blue, then a teaspoon of green, then a teaspoon of yellow, etc. Or, you can alternate cupcakes, starting with red on bottom and ending with purple on top like I did. Do NOT swirl the colors together. It's okay if the colors don't completely line up; this is what makes them look unique and cool! Swirling, however, may muddy the colors.
  • Bake for 15-18 minutes or until a toothpick inserted near the center comes out clean or with moist, but not wet, crumbs. Cool completely.
  • For the buttercream: In a large mixing bowl, beat together the butter and vanilla until smooth. Gradually add in the confectioners' sugar, one cup at a time, alternating with the heavy cream until frosting is light and fluffy.
  • Pipe or spread the frosting onto the cooled cupcakes. Garnish with rainbow sprinkles or sour rainbow candy belts cut in half and arced onto the cupcake frosting.