Preheat your oven to 350°F (175°C). Grease and flour two 8-inch round cake pans, then line the bottoms with parchment paper. This helps prevent sticking and makes removal easier.

In a large bowl, whisk together the sifted all-purpose flour, granulated sugar, baking powder, and salt until well combined. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), cream the softened unsalted butter on medium speed for about 2 minutes, until light and fluffy.

Add the eggs one at a time, beating well after each addition. Scrape down the sides of the bowl as needed. Beat until the mixture is light in color and fluffy, about 2-3 minutes.

In a separate small bowl, combine the room temperature whole milk and pure vanilla extract.

With the mixer on low speed, gradually add about one-third of the dry ingredients to the butter mixture, mixing until just combined. Then, add half of the milk mixture, mixing until just combined. Repeat with another third of the dry ingredients, the remaining milk mixture, and finally the last third of the dry ingredients. Mix until just incorporated, being careful not to overmix. Overmixing can lead to a dense cake.

Divide the batter evenly between the two prepared cake pans. Smooth the tops with a spatula.

Bake for 28-32 minutes, or until a wooden skewer inserted into the center of the cakes comes out clean. The tops should be lightly golden and spring back when gently touched.

Remove the cakes from the oven and let them cool in their pans on a wire rack for 10-15 minutes. Then, invert the cakes onto the wire rack, remove the parchment paper, and let them cool completely before frosting (at least 1 hour).

In the bowl of a stand mixer fitted with the paddle attachment, beat the softened unsalted butter on medium-high speed for 3-5 minutes, until very light and fluffy. This step is crucial for light buttercream.

With the mixer on low speed, gradually add the sifted powdered sugar, 1 cup at a time, until fully incorporated. Once all sugar is added, increase speed to medium-high and beat for another 2-3 minutes.

Add the pure vanilla extract, heavy cream (or milk), and a pinch of salt. Beat on medium-high speed for another 2-3 minutes, scraping down the sides of the bowl, until the buttercream is light, fluffy, and smooth. If too thick, add more cream 1 tablespoon at a time; if too thin, add more powdered sugar 1/4 cup at a time.

Once the cakes are completely cool, place one cake layer on your serving plate or cake stand. If desired, you can level the tops of the cakes with a serrated knife for a flatter surface.

Spread about 1/2 to 3/4 cup of vanilla buttercream evenly over the first cake layer. Carefully place the second cake layer on top.

Use the remaining buttercream to frost the top and sides of the entire cake. Decorate as desired.