Preheat to 350°F. Grease 3- 8 inch round cake pans. line each with circular parchment paper, and then grease and flour the parchment paper and the bottom and sides of the pans. Set aside
Sift the flour, baking powder, baking soda, and salt into a medium sized bowl. Set aside.
Cream the butter and sugar on medium speed in a stand mixer fitted with a paddle attachment for 2-3 minutes. The butter and sugar will appear light and fluffy.
Add the eggs, one at a time, beating after each addition for 30- 60 seconds. Scrape down the sides of the bowl as needed.
Add the clear vanilla extract and mix until combined.
With the mixer on low, alternately add the flour mixture and the buttermilk, starting and finishing with the flour. Mix until just combined.
Fold in the sprinkles.
Evenly distribute the batter amongst the 3 pans. Bake for 26-30 minutes or until a toothpick inserted in the center comes out clean.
Remove the cake pans from the oven and set on a wire rack for 10 minutes. After the 10 minutes, turn the cakes out of the pans and allow to cool completely before frosting.
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter on medium high speed for about 2 minutes.
Add the powdered sugar, vanilla, and salt. Mix. Add the heavy cream 1 T. at a time, until you reach your desired consistency.
To assemble. Place a generous amount of frosting on one of the cakes, spread until it's in an even layer. Add a second cake to the top of the frosting. Add a generous amount of frosting to the top of the cake and spread until the top of the cake is evenly covered.
Finish by placing the third and final cake atop of the frosting. Do a thin crumb coat on the top and along the outside of the entire cake. Place the cake in the fridge (or freezer) for 15 minutes to set the crumb coat.
Remove from the fridge or freezer and add the remaining frosting to the top and sides of the cake. Add sprinkles or additional decorations.