Funfetti Birthday Cake

Steps

1. Preheat the oven to 175°C (350°F). Grease a 23 cm (9-inch) round cake pan and line the bottom with parchment paper.
2. In a medium bowl, whisk together the all-purpose flour, baking powder, and 3 g of the fine salt until evenly combined.
3. In a large mixing bowl, beat 140 g of the unsalted butter at 20–22°C with the granulated sugar for 3–4 minutes, until very pale, creamy, and fluffy.
4. Beat in the eggs one at a time, mixing well after each addition and scraping down the bowl so the batter is smooth and homogeneous.
5. In a small jug, whisk together 180 ml of the whole milk with 5 ml of the vanilla extract. This liquid mixture should be at 20–22°C.
6. Add one-third of the dry ingredients to the butter mixture and mix on low just until incorporated. Add half of the milk mixture and mix briefly. Repeat, finishing with the last third of the dry ingredients, mixing only until a smooth, thick, creamy batter forms. Do not overmix to keep the crumb soft and tender.
7. Fold 80 g of the rainbow sprinkles gently into the batter until evenly distributed, being careful not to overmix or streak the colors.
8. Scrape the batter into the prepared pan and smooth the top evenly with a spatula so it bakes level.
9. Bake for 28–32 minutes, until the top is lightly golden, the edges look set, the center springs back softly when gently pressed, and a toothpick inserted in the center comes out clean or with a few moist crumbs attached.
10. Let the cake cool in the pan for 10 minutes, then carefully turn it out onto a wire rack. Remove the parchment and cool completely to room temperature (20–22°C) so the frosting will not melt.
11. For the frosting, place the remaining 120 g unsalted butter at 20–22°C in a clean bowl with the remaining 1 g fine salt. Beat for 1–2 minutes until smooth and creamy. Gradually add the powdered sugar while beating on low, then increase to medium and beat until thick, light, and fluffy. Add the remaining 5 ml vanilla extract and 30 ml of the whole milk, then beat for 2–3 minutes until the frosting is very smooth, airy, and spreadable.
12. Place the fully cooled cake on a serving plate. Spread the vanilla frosting generously over the top and sides of the cake, creating soft swirls for a fluffy, cloudlike finish. Sprinkle the remaining 20 g rainbow sprinkles evenly over the top. The finished cake should have a soft, fluffy, moist crumb with a light, creamy frosting and vibrant sprinkles in every slice.