Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line them with parchment paper. This ensures your cake releases cleanly after baking.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside. These dry ingredients will give the cake structure and lightness.

In a large mixing bowl, using a stand or hand mixer, beat the softened butter and granulated sugar together on medium-high speed until pale, light, and fluffy—about 3-5 minutes. This step is key to creating an airy texture.

Add the eggs one at a time, beating well after each addition. Scrape down the sides of the bowl to ensure even mixing. Stir in the vanilla extract.

With the mixer on low speed, add the flour mixture in three parts, alternating with the buttermilk in two parts. Begin and end with the flour mixture. Mix just until combined—do not overbeat.

Divide the batter evenly between the prepared pans. Tap them gently on the counter to remove air bubbles. Bake for 25–30 minutes or until a toothpick inserted in the center comes out clean. Cool in pans for 10 minutes, then transfer to wire racks to cool completely.

In a large bowl, beat the butter until creamy. Gradually add the sifted powdered sugar, one cup at a time, beating well on medium speed. Add vanilla extract and a pinch of salt. Add cream or milk 1 tablespoon at a time, until desired consistency is reached. Beat until fluffy—about 3–5 minutes.

Place one cake layer on a serving plate. Spread a generous amount of frosting on top. Place the second cake layer over it and frost the top and sides. Use an offset spatula for smooth application.