1. Preheat your oven to 325°F. Grease and flour three 8-inch round cake pans. Place a circle of parchment or wax paper on the bottom of each pan.
2. In a medium bowl, whisk together the cake flour, baking powder, baking soda, and salt for 30 seconds. Set aside.
3. In another bowl, combine the buttermilk, vegetable oil, and vanilla extract. Set aside.
4. In the bowl of a mixer, add the softened butter and cream cheese. Mix on medium speed until smooth and creamy.
5. Gradually add the sugar, continuing to mix on medium speed for 2-3 minutes until light and fluffy.
6. Add the eggs one at a time, mixing until each egg is fully incorporated before adding the next.
7. With the mixer on low speed, alternate adding the flour mixture and the buttermilk mixture to the batter, starting and ending with the flour mixture. Be careful not to over-mix.
8. Divide the batter evenly among the prepared pans. Bake for 25-28 minutes, or until a toothpick inserted into the center of the cakes comes out clean.
9. Allow the cakes to cool in the pans for 5-10 minutes, then turn them out onto a wire rack to cool completely.

**Vanilla Buttercream:**

1. Cream the softened butter until smooth. Add the vanilla extract and blend well.
2. Gradually add half of the powdered sugar and most of the milk. Beat on medium speed until fully combined.
3. Add the remaining powdered sugar and milk, mixing for another 3-4 minutes. Occasionally scrape down the sides of the bowl. Reduce the mixer speed to low and beat for 1-2 minutes to eliminate any air pockets, creating a smooth texture.

**Assembly:**

1. Place the first cake layer on your cake plate or pedestal. Spread a layer of buttercream on top.
2. Add the next two cake layers, spreading buttercream between each layer.
3. Apply a thin crumb coat of buttercream over the entire cake. Chill the cake in the freezer for 10-15 minutes, or longer in the refrigerator, until the frosting is firm.
4. Apply a final coat of buttercream and smooth it out with a spatula or bench scraper. If desired, decorate with borders or piping.