Rainbow Sprinkle Cake Recipe

Prepare

Preheat the oven to 350°F (175°C). Grease and line two 8-inch (or three 6-inch) round cake pans with parchment paper; lightly butter the sides.

In a medium bowl, whisk together the all-purpose flour, baking powder, and salt until evenly combined. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), cream 1 cup room-temperature unsalted butter and 1.5 cups granulated sugar on medium-high speed for 3–4 minutes, until light and fluffy and slightly pale.

Add the eggs one at a time, mixing 20–30 seconds after each addition until incorporated. Scrape the bowl as needed. Mix in 2 teaspoons vanilla extract.

With the mixer on low, add one-third of the dry flour mixture, then half of the milk (about 1/2 cup), mix until just combined. Add another third of the dry ingredients, the remaining milk, then finish with the last third of dry ingredients. Do not overmix; stop as soon as no streaks of flour remain.

In a small bowl, toss 3/4 cup rainbow sprinkles with 1 tablespoon of flour from the measured dry ingredients (this helps prevent bleeding/sinking). Gently fold the coated sprinkles into the batter with a spatula until evenly distributed.

Divide the batter evenly between the prepared pans (use a scale or eyeball). Smooth the tops. Bake in the preheated oven until a toothpick inserted in the center comes out with a few moist crumbs, about 22–28 minutes for 8-inch pans (shorter for 6-inch).

Remove cakes from oven and allow to cool in pans for 10 minutes. Run a knife around the edges, then invert onto a wire rack and remove parchment. Cool completely before filling and frosting, about 1–2 hours.

If the cake layers are domed, level the tops with a serrated knife or cake leveler so the layers stack evenly. Place one cake layer on a serving plate or cake board.

Spread about 1/2 cup of strawberry jam evenly over the top of the bottom layer, leaving a small 1/4-inch gap at the edge to prevent jam from squeezing out. If jam is very loose, gently heat it for 10–15 seconds in the microwave and stir to slightly thicken before using.

Place the second cake layer on top of the jam. If making three layers, spread jam on the first and second layers (use remaining jam as needed). Chill the stacked layers in the refrigerator for 10 minutes to set the jam and make crumb-coating easier.

While the cake chills, make the buttercream. In a clean bowl, beat 1 cup room-temperature unsalted butter on medium speed until creamy, about 1–2 minutes.

Gradually add 4 cups sifted confectioners' sugar, about 1 cup at a time, mixing on low speed to avoid powdered sugar clouds. Once incorporated, add 1 teaspoon vanilla extract, 1/4 teaspoon salt, and 2 tablespoons heavy cream. Increase mixer speed to medium-high and beat for 2–3 minutes until light and fluffy. Adjust consistency: add the remaining tablespoon of cream if too stiff, or add more sifted sugar if too loose.

Remove the cake from the refrigerator. Apply a thin crumb coat of buttercream (about 3/4 cup) over the top and sides to trap crumbs. Smooth with an offset spatula. Chill the cake in the refrigerator for 15–20 minutes until the crumb coat is set.

Apply a final thicker layer of buttercream, smoothing the top and sides. Use an offset spatula or bench scraper to get clean edges. Reserve a small handful of sprinkles to press into the side or top if desired.

Press additional rainbow sprinkles (about 1/2 cup) onto the bottom edge and/or top of the cake as decoration. For a confetti-studded cut, sprinkle a few extra jimmies on the top center.

Refrigerate the finished cake for 15–30 minutes to set the frosting before slicing. Bring to room temperature for 20–30 minutes before serving for best texture.