Preheat your oven to 350°F (175°C). Grease and flour two 8-inch round cake pans or a 9x13 inch pan. Line the bottoms with parchment paper for easy removal.
In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Set aside.
In a large mixing bowl, cream together the softened unsalted butter and granulated sugar on medium-high speed until light and fluffy, about 3-5 minutes.

Add the eggs one at a time, beating well after each addition until fully incorporated. Stir in the vanilla bean paste or extract.
Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk. Begin and end with the dry ingredients (e.g., flour, buttermilk, flour, buttermilk, flour). Mix on low speed just until combined after each addition. Be careful not to overmix.
Divide the batter evenly between the prepared cake pans. Smooth the tops with a spatula.
Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean. Baking time may vary slightly.
Let the cakes cool in the pans on a wire rack for 10-15 minutes before inverting them onto the rack to cool completely before frosting.