Rainbow Sprinkle Cake Recipe

Prepare and preheat

Preheat oven to 350°F (175°C). Grease and line two 8-inch (20 cm) round cake pans with parchment paper; lightly grease the parchment and dust pans with flour, tapping out excess.

Whisk dry ingredients

In a medium bowl, whisk together 2.5 cups all-purpose flour, 2 tsp baking powder, and 1/2 tsp salt. Set aside.

Cream butter and sugar

In a large bowl or stand mixer fitted with the paddle attachment, beat 3/4 cup room-temperature unsalted butter and 1.75 cups granulated sugar on medium-high speed for 3–4 minutes until light and fluffy and pale in color.

Add eggs and vanilla

Add the 4 large eggs one at a time, beating well after each addition. Scrape the bowl as needed. Mix in 2 tsp vanilla extract.

Alternate dry and wet

With the mixer on low, add one-third of the dry ingredients, then half of 1 cup whole milk, then another third of dry, then the remaining milk, then the last third of dry. Mix just until combined after each addition—avoid overmixing.

Add oil and sprinkles

Mix in 2 tbsp vegetable oil until incorporated (this keeps the cake moist). Using a rubber spatula, gently fold in 3/4 cup rainbow sprinkles until evenly distributed. Fold just enough to combine so the sprinkles do not bleed color into the batter.

Bake

Divide batter evenly between the prepared pans, smoothing the tops. Bake in the preheated 350°F (175°C) oven for 22–28 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs and the cake springs back when lightly pressed.

Cool

Allow cakes to cool in the pans for 10 minutes, then run a knife around the edges and invert onto a wire rack. Peel off parchment and let layers cool completely (about 1 hour). Cooling completely prevents the jam and frosting from melting.

If your strawberry jam is very loose, warm it briefly in a small saucepan over low heat or microwave in 20-second bursts to thicken slightly so it spreads without running. If desired, stir in 1–2 tbsp of crushed fresh strawberries for texture. Let the jam cool to room temperature before assembling.

Optional: For a neater barrier, spread a thin dam of frosting around the edge of the bottom cake layer before adding jam; this helps keep the jam from oozing out of the sides.

Make the frosting

In a large bowl or stand mixer, beat 1 cup room-temperature unsalted butter on medium speed for 1–2 minutes until smooth. Gradually add 4 cups powdered sugar, about 1 cup at a time, mixing on low until incorporated. Add 1 tsp vanilla extract, 1/4 tsp salt, and 4 tbsp heavy cream or whole milk. Increase speed to medium-high and beat 2–3 minutes until light, fluffy, and spreadable. If frosting is too thick, add an extra tsp of cream; if too thin, add up to 1/2 cup more powdered sugar.

Level and assemble layers

If the cake layers have domes, trim them with a serrated knife to create level surfaces. Place one layer on a cake board or serving plate. If using, spread a thin ring (about 1/4-inch high) of frosting around the edge of the layer to form a dam. Spoon and spread 1 cup of prepared strawberry jam into the center of the bottom layer, keeping within the frosting dam so it does not leak.

Stack and crumb coat

Place the second cake layer on top. Apply a thin crumb coat of frosting over the top and sides to seal in crumbs (about 1/4-inch layer). Chill the cake in the refrigerator for 20–30 minutes to set the crumb coat.

Final frost and decorate

Apply a final, even layer of frosting over the chilled cake using an offset spatula. Press 1/4 cup rainbow sprinkles onto the sides and scatter or press additional sprinkles on top as desired. For a clean look, rotate the cake on a turntable while applying sprinkles to the sides.

Chill before serving

For easiest slicing, chill the frosted cake for 20–30 minutes to firm the frosting. Let sit at room temperature 10–15 minutes before serving so the cake is soft and the flavor is optimal.