1.     Prepare the Cake: Preheat your oven to 350°F (175°C). Coat three 8-inch round cake pans with baking spray and line the bottoms with parchment paper for easy removal.

2.     Mix the Batter: Mix the softened butter and white sugar together in a mixer with a paddle attachment. Beat at medium speed for about four minutes until the mixture becomes light and fluffy. Add the eggs one at a time, mixing on low speed until fully incorporated.

3.     Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add this flour mixture to the butter-sugar mixture, alternating with the milk. The flour mixture is the first thing to be added, mixing until just combined. Finally, add the vanilla extract and sprinkles, mixing gently for about 20 seconds.

4.     Bake the Cake: Divide the batter equally between the prepared pans. Bake 25-28 minutes or until toothpicks inserted at the center come out clean.

5.     Cool the Cakes: Once baked, let the cakes cool in the pans for 10 minutes. Then, invert them onto a wire rack to cool completely, approximately 30 minutes.

6.     Prepare the Frosting: In the clean stand mixer, beat the softened butter until creamy. Gradually add the powdered sugar, salt, and vanilla extract. Mix on low speed until combined, then add the sour cream and beat at high speed until fluffy, scraping down the sides as needed.

7.     Assemble the Cake: Spread generous amounts of frosting over top. Repeat this procedure with the second layer. Place the final layer on top and spread the remaining frosting over the top and sides of the cake. Garnish with additional sprinkles.

8.     Serve and Enjoy: Slice the cake and serve it at room temperature for the best flavor. Enjoy the colorful celebration!