Pre-heat the oven to 350°F.
Spray two 9-inch round cake pans with baking spray; dust pans with flour; line bottoms of pans with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, beat butter and sugar at medium speed until fluffy; 3 to 4 minutes, stopping to scrape sides of bowl.
Add eggs, one at a time, beating well after each addition; add vanill and beat to combine.
In a large bowl, whisk together flour, baking powder, salt and baking soda.
Add flour mixture to butter mixture alternately with buttermilk, beginning and ending with flour mixture, beating until well combined after each addition.
Divide batter between prepared pans; using a small offset spatula, smooth tops.
Forcefully tap pans on counter several times to evenly spread batter and release air bubbles.
Place in the pre-heated oven and bake until a wooden pick inserted in center comes out clean; about 35 minutes.
Remove from the oven, place on a wire racks and allow to cool for 10 minutes.
Remove cakes from the pans; allow to cool completely, parchment side down, on wire racks.
Level cake layers, if desired; discard parchment.
Place 1 cake layer on a serving plate.
Spoon 2-½ cups of the Creamy Vanilla Frosting into a large piping bag fitted with a ½-inch round piping tip.
Pipe frosting evenly over cake layer; smooth with a small offset spatula.
Place remaining cake layer on top.
Spoon another 2-½ cups of the frosting into a piping bag.
Pipe evenly over top of cake; using a small offset spatula, smooth into an even layer.
Spoon remaining frosting into a piping bag.
Pipe all over the sides of the cake; holding a bench scraper or a large offset spatula against sides of the cake, scrape off excess frosting until sides are smooth and layers are somewhat exposed.
Pile excess frosting on top of the cake; using the back of a spoon or a large offset spatula, spread and swirl frosting as desired.
Using a bench scraper or a large offset spatula held against the cake layers, scrape frosting one more time to give sides a smooth, finished look.