Preheat your oven to 350°F (175°C). Grease and flour two 8-inch round cake pans and line the bottoms with parchment paper.

In a large bowl, whisk together the sifted all-purpose flour, granulated sugar, baking powder, baking soda, and salt.

In a separate medium bowl, whisk together the buttermilk, vegetable oil, eggs, and 1 tablespoon vanilla extract until well combined.

Add the wet ingredients to the dry ingredients, mixing on low speed with an electric mixer until just combined. Do not overmix. Scrape down the sides of the bowl.

Pour the batter evenly into the prepared cake pans. Gently tap the pans on the counter a few times to release air bubbles.

Bake for 28-32 minutes, or until a wooden skewer inserted into the center comes out clean.

Remove cakes from the oven and let cool in the pans on a wire rack for 10-15 minutes.

Carefully invert the cakes onto the wire rack, remove parchment paper, and let cool completely before frosting.

To make the vanilla buttercream: In a large bowl, cream 1 cup softened unsalted butter with an electric mixer on medium speed until light and fluffy (3-4 minutes).

Gradually add the sifted powdered sugar, about 1 cup at a time, mixing on low speed until incorporated before increasing to medium-high. Continue until all sugar is added and the mixture is fluffy.

Beat in 2 teaspoons vanilla extract and 2 tablespoons milk. If the frosting is too thick, add more milk, one teaspoon at a time, until smooth and spreadable.

Once cakes are completely cool, level them with a serrated knife if necessary. Place one layer on your serving plate or cake stand.

Spread about 1 cup of buttercream evenly over the first cake layer. Place the second layer on top and repeat with another cup of frosting.

Use the remaining buttercream to frost the sides and top of the entire cake, smoothing with an offset spatula. Decorate as desired.