Have all ingredients at room temperature.
Preheat the oven to 350 degrees. Butter and flour your pans and set them aside.
Using a stand mixer, use the paddle attachment and whip the butter until smooth, about 4 minutes, scraping the sides of the bowl after each minute. Add the sugar and beat on medium-high for about 2 minutes. Scrape the sides of the bowl again. Add in the vanilla.
Crack eggs one by one into a separate small bowl in case a shell gets in or you have a bad egg, you won't compromise the whole batter. With the mixer on low, add the eggs in one at a time.
In a separate bowl, combine the flour, baking powder, baking soda, and sea salt. Mix to incorporate with a fork.
With the mixer on low speed, add half of the flour mixture. When it's incorporated, add half of the buttermilk. Add in the remainder of the flour and add in the remaining buttermilk. Scrape down the sides of the bowl and mix until smooth. Using a spatula, add in the sprinkles.
Place the prepared cake pans onto a baking sheet. Evenly distribute the batter among the cake pans. Place in preheated oven and bake until a toothpick inserted comes out clean. About 30-35 minutes. Carefully rotate the pan halfway through baking. Remove onto a wire rack and cool. If the tops are not level, you may use a serrated knife to cut and make them level. Using an offset spatula, evenly ice the cake and immediately press the sprinkles onto the cake. If you wait, the icing will harden on the outside, and the sprinkles will fall off.