How to Make the Easiest (and Cutest!) Baby Shower Cake Ever

You’d never believe how easy this adorable onesie cake is. No special pans. No carving skills required. Just a classic, rectangular baking dish and a few simple tools are all you’ll need to create this cake cutie.

Make a sweet and simple onesie cake!

Onesie Cake | Erin Gardner

Bonus tip: Looking for a creative take on a gender reveal cake? Tint the cake batter the correct color before baking and finish the cake in gender-neutral tones.


  • Rectangular cake
  • Small knife
  • Buttercream
  • Star sprinkles (or ones that match your event)
  • Parchment paper
  • Small round piping tip
  • Piping bag

Step 1:

Trim the top of your cake flat and flip it onto a platter. I baked my cake in a 15″ x 10″ glass baking dish, but the technique will work with any rectangular cake. A tiny bit of my cake stuck to the bottom of the pan and I have a little crack from flipping it out. Not to worry! Buttercream will come to the rescue!

Rectangular cake | Erin Gardner

Step 2:

Cut a half circle from the middle of one of the short ends of the cake. This will be the onesie’s neck hole.

Then, cut the corners off the opposite end of the cake to make the onesie’s leg holes. Make your cuts slightly arched, not straight across.

Trimming the cake | Erin Gardner

Step 3:

Discard (or nibble on) the neck cut-out, but save the leg cut-outs to make the onesie’s sleeves. Trim the arched sides of the corners so they’re flat. Place the cut edges against the sides of the cake, lining the corners up with the top edge of the cake. You now have your onesie’s shape!

Placing the sleeves | Erin Gardner

Step 4:

Ice the cake with buttercream frosting and coat the freshly iced surface with a layer of sprinkles. I used bright star sprinkles, but you can use any color or shape of sprinkles you like.

Iced onesie | Erin Gardner Onesie with sprinkles | Erin Gardner

Then, place a piece of parchment paper on top of the cake. Run your hands over the paper, gently pressing the sprinkles into the buttercream. Doing this will give you a smooth, even surface to pipe the onesie’s details.

Smoothing out the sprinkles | Erin Gardner

Step 5:

Fill a piping bag fitted with a small round tip with buttercream. Pipe a few details onto the surface of your cake:

  • Outline the onesie
  • Embellish the neck and sleeves with additional lines
  • Add a curved line and dots for snaps at the bottom of the onesie
Piped details | Erin Gardner

Step 6:

Personalize your onesie by adding a name or special message.

Finished onesie cake | Erin Gardner

How easy was that? You’ll definitely want to keep this idea on hand. Save this tutorial to Pinterest so you can find it later!

Easy Onesie Cake

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4 Responses to “How to Make the Easiest (and Cutest!) Baby Shower Cake Ever”

  1. Brenda Osgood

    Going to try this , what a great idea

  2. Cynthia

    The directions were simple and the cake was the cutest!

  3. Elizabeth Wairimu


  4. Susan

    Onesie cake