Preheat your oven to 350°F (175°C). Grease and flour two 8-inch round cake pans, or line with parchment paper circles and spray with baking spray.
In a medium bowl, whisk together the sifted cake flour, granulated sugar, baking powder, and salt. Set aside.
In a large bowl, using an electric mixer on medium speed, cream the softened butter until light and fluffy. Scrape the seeds from the vanilla beans and add them to the butter, beating for another minute until well incorporated.
Add the eggs one at a time, beating well after each addition until fully incorporated. Scrape down the sides of the bowl as needed.
With the mixer on low speed, gradually add the dry ingredients to the wet ingredients in three additions, alternating with the buttermilk in two additions. Begin and end with the dry ingredients. Mix just until combined; do not overmix.
Divide the batter evenly between the prepared cake pans. Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean and the tops are golden brown.
Let the cake layers cool in the pans for 10-15 minutes before inverting them onto a wire rack to cool completely. Ensure they are fully cool before frosting.
For the frosting: In a large bowl, cream the softened butter with an electric mixer until light and fluffy. Gradually add the sifted powdered sugar, alternating with heavy cream or milk, mixing until smooth and creamy. Beat in the vanilla extract.
Once cakes are completely cool, frost the layers and top of the cake. Decorate as desired.