Rainbow Swirl Cupcakes
Super soft and moist vanilla cupcakes topped with a swirl of rainbow-colored vanilla buttercream. So whimsical and fun to make!
Servings 14 cupcakes
Equipment
Ingredients
Vanilla Cupcakes
- 1 1/4 cups (132g) sifted cake flour* DIY recipe in notes
- 1 tsp baking powder
- 1/4 tsp baking soda
- 1/2 tsp salt
- 6 Tbsp (82g) unsalted butter, softened to room temperature
- 2 Tbsp (30ml) vegetable oil
- 3/4 cup (150g) granulated white sugar
- 2 large eggs, room temperature
- 2 Tbsp (30g) sour cream, room temperature
- 1 1/2 tsp pure vanilla extract
- 1/2 cup (120ml) whole milk, room temperature
Rainbow Vanilla Buttercream
- 1 Cup (226g) unsalted butter, room temperature
- 3 1/2 Cups (420g) powdered sugar
- 2 Tbsp whole milk, room temperature
- 2 tsp pure vanilla extract
- 1/4 tsp salt, or to taste
- 1-2 drops pink food coloring
- 1-2 drops yellow food coloring
- 1-2 drops blue food coloring
- 1-2 drop purple food coloring
Instructions
Make the Vanilla Cupcakes
- Preheat the oven to 350°F (177ºC) and line standard cupcake pan(s) with liners. This recipe makes about 14 cupcakes.
- Add the sifted cake flour, baking powder, baking soda, and salt into a bowl and whisk to combine. Set aside.
- In the bowl of your stand mixer fitted with the paddle attachment (or with an electric mixer and large bowl), beat the butter on high for two minutes until creamy. Add the vegetable oil and sugar and continue to mix on high for another two minutes. Scrape down the bowl and paddle. Turn the mixer to low speed and add the eggs one at a time, mixing thoroughly after each addition. Add the vanilla and sour cream, then turn the mixer to high speed and mix for one minute. Scrape down the bowl and paddle as needed.
- With the mixer on low speed, add in the dry ingredients all at once and mix until just combined, then add the milk in a steady stream. Continue mixing for another 20-30 seconds, until just combined. Scrape down the sides and bottom of the bowl and give it a few stirs to make sure there are no lumps (without over-mixing). The batter will be slightly thick.
- Spoon or pour the batter into the cupcake tins until they’re about ⅔ full, then bake for 14-18 minutes, until they spring back to the touch and a toothpick inserted into the middle comes out clean. Let the cupcakes cool in the pan for about five minutes before removing them from the pan and continuing to cool on a wire rack until room temperature. Make sure they are entirely room temperature before adding any frosting.
Make the Vanilla Buttercream
- With a hand mixer or paddle attachment on your stand mixer, cream the butter on medium-high until it’s creamy and light (almost white) in color. About 7 minutes.
- With the mixer on low, add the sifted powdered sugar one cup at a time, scraping down after each addition and making sure each cup is fully incorporated before adding the next one. Add vanilla, milk, and salt and mix on low for another minute until fully incorporated.
- Color the Buttercream: divide the vanilla buttercream between four bowls. Add the pink food coloring to the first bowl and mix it in. Repeat with the other three bowls and the yellow, blue, and purple food coloring.
Assembly
- Prepare the Rainbow Piping Bag: Spread a piece of plastic wrap onto a flat surface and pipe or spoon the pink buttercream onto it in a straight line. Next to the pink, pipe or spoon the yellow buttercream in a straight line and repeat the process with the blue and purple buttercream. See the picture in the blog post above for reference.
- Roll up the plastic wrap so that the pink and purple buttercream end up on top of one another. Continue rolling until the plastic wrap encloses the buttercream in a tube, then snip off the end. Place the buttercream tube into a piping bag fitted with Wilton Tip 1M with the cut end facing down.
- Pipe the Rainbow Swirls: Starting in the center of the cupcake, squeeze the piping bag while pulling it up about ½ inch from the cupcake surface, then continue squeezing while you move the piping bag to the left and swirl it around the edge in a counter-clockwise rotation. Once you’ve made a full rotation, gently release the pressure on the piping bag while quickly pulling the bag counter-clockwise. This will create the pointed end of the rainbow swirl. Repeat until each cupcake is topped with a rainbow swirl.
Notes
*DIY Cake Flour Recipe: To make your own cake flour, spoon and level one cup of all-purpose flour and remove 2 Tbsp. Add 2 Tbsp of cornstarch. Repeat per the amount of cake flour you need, then sift the flour and cornstarch mixture 4 times (don't skip that step!). After sifting, spoon and level to re-measure the amount of cake flour you need. Keep in mind that if you do use the homemade version, the gram measurement will weigh more (295g instead of 265g) since all-purpose flour is heavier than cake flour.
Make Ahead Tips:
- The vanilla cupcakes can be baked, cooled, stored in their cupcake pan with plastic wrap over the top, and left out at room temperature up to one day ahead of decorating. Unfrosted cupcakes can be stored in an airtight container in the freezer for up to one month before thawing and frosting.
- The vanilla buttercream can be made ahead and stored at room temperature in an airtight container for up to one day, or in an airtight container in the refrigerator for up to two weeks. When you’re ready to use it, bring it back to room temperature and re-whip in your stand mixer to bring back to smooth buttercream consistency.
- Once decorated, the rainbow swirl cupcakes can be stored at room temperature for up to 4 days.