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First Birthday Smash Cake

*Total Time includes roughly 45 minutes of cooling/chilling time.
Celebrate your baby’s first birthday with this soft and simple smash cake — refined sugar-free, naturally sweetened, and perfect for little hands. Easy to make gluten- and dairy-free, too!
Total Time 2 hours
Servings 1 three-layer, 4-inch cake
Author Rachael DeVaux

Equipment

Ingredients

For the cake:

  • 2 ripe bananas, mashed (~1 cup)
  • ¼ cup unsweetened applesauce
  • ¼ cup peanut butter (ingredients should be just peanuts + salt) or substitute sunflower seed butter
  • 2 eggs
  • ¼ cup full-fat coconut milk or whole milk
  • 1 teaspoon vanilla extract
  • 1¼ cups oat flour (I like Bob’s Red Mill GF Oat Flour) or 1 cup almond flour and ¼ cup coconut flour
  • 1 teaspoon baking powder
  • ½ teaspoon cinnamon
  • Pinch of sea salt

For the frosting:

  • ¾ cup plain full-fat Greek yogurt or coconut yogurt for dairy-free
  • 2 tablespoons peanut butter (ingredients should be just peanuts + salt)
  • 1 –2 tablespoons unsweetened applesauce optional for sweetness
  • ½ teaspoon vanilla extract

Toppings:

  • Fresh raspberries (or favorite fruit) to line the outside

Instructions

  • Preheat the oven to 325°F. Grease and line three 4-inch cake pans (buy on Amazon HERE!) with parchment rounds. To make parchment rounds, simply trace the bottom of your cake pans onto a sheet of parchment paper, then cut along the lines with scissors. Place each round into the bottom of the greased pans to prevent sticking and make for easy release once baked.
  • Mash the bananas in a mixing bowl. Stir in applesauce, peanut butter, eggs, milk, and vanilla.
  • Add oat flour, baking powder, cinnamon, and salt. Mix just until combined.
  • Let the batter rest for 5–10 minutes so the oat flour can absorb moisture.
  • Divide batter evenly among your pans, aiming for just under halfway full.
  • Bake (at 325°F) for 30–35 minutes, or until a toothpick comes out with a few moist crumbs.
  • While the cake is in the oven, prepare the frosting: in a mixing bowl, stir together the Greek yogurt, peanut butter, applesauce (if using), and vanilla extract until smooth and creamy. Place the frosting in the refrigerator to chill and thicken while the cake cools.
  • Once the cakes are done baking, remove from the oven and allow them to cool in the pans for 15 minutes.
  • After cooling, gently remove each layer from its tin and transfer to a plate or wire rack. Chill the layers in the fridge for at least 30 minutes, or until completely cooled.
  • Once chilled, use a serrated knife to carefully trim the domed tops off each cake layer. This will help your cake stack evenly and stay stable.
  • Place one cake layer on a small serving plate or cake board. Add a spoonful of frosting on top and spread it evenly with an offset spatula or the back of a spoon. Repeat with the second and third layers.
  • Time to frost: use the remaining frosting to cover the top and sides of the cake. A light "naked cake" style works beautifully here, but you can go fully frosted for a smoother finish. Chill again briefly to help it set, if needed.
  • Option to add toppings: decorate with baby-safe favorites like fresh raspberries, banana slices, or a soft birthday candle. Enjoy!

Storage Tips:

  • Leftovers: store in an airtight container in the fridge for up to 3 days.
  • Make-Ahead: bake the cake layers 1–2 days in advance. Wrap each cooled layer tightly in plastic wrap or glass Tupperware and store in the fridge. Frost the cake the day of serving for best texture and appearance.
  • Freezer option: unfrosted cake layers can be frozen for up to 1 month. Thaw overnight in the fridge before assembling.

Notes

This recipe is already gluten-free, but here are some options to keep it nut-free, dairy-free, and grain-free if needed:
  • Peanut butter → Sunflower seed butter (look for one with just seeds + salt) works for a nut-free option
  • Milk → Use full-fat coconut milk to keep it dairy-free, or whole milk if no dairy sensitivities or allergies
  • Oat flour → For a grain-free version, swap 1 cup almond flour + ¼ cup coconut flour for the oat flour (note: this swap still tastes great, but will be less fluffy than the oat flour)
  • Greek yogurt (for frosting) → I used full-fat Greek yogurt, but coconut yogurt is great for a dairy-free option
  • Applesauce → make sure you use an unsweetened one. For the frosting, it’s optional, but adds extra natural sweetness if desired.
To keep the frosting super simple, just frost with Greek yogurt (or coconut yogurt) without the applesauce and vanilla extract – that’s what I did, and Hayes loved it!