1- First, preheat oven to 180°C (350°F) and position the rack in the middle. Grease and line two 20cm (8 inch) cake pans with parchment paper to prevent sticking. In a large bowl, whisk together flour, baking powder, and salt to combine the dry ingredients uniformly.

2- Next, beat eggs at medium speed for 30 seconds, then gradually add sugar over 45 seconds while mixing. Continue beating eggs and sugar at high speed for 7 minutes until the mixture triples in volume and becomes white and glossy, which is essential for a light texture.

3- Heat the butter and milk together until the butter melts; do not boil. Add the flour to the whipped egg mixture in three parts, mixing briefly at low speed just to incorporate. Into the empty flour bowl, pour the melted butter and milk mixture, vanilla extract, and oil, then add about 1 1/2 cups of the whipped egg batter to the hot milk mixture and whisk until smooth and foamy.

4- Gently combine the milk mixture back into the egg batter at low speed, scrape the sides and bottom, mixing briefly until smooth and pourable. Divide the batter evenly between the prepared pans and drop the pans gently on the counter three times to release large air bubbles.

5- Bake for about 30 minutes or until the cakes are golden and a toothpick inserted in the center comes out clean. Cool the cakes in pans for 15 minutes, then remove onto wire racks to cool completely and invert the cakes if layering to achieve a flat surface. Finally, frost with vanilla buttercream once completely cool.

6- For the frosting, beat softened butter at high speed until pale and fluffy (about 3 minutes). Gradually add sifted icing sugar in three parts, mixing slowly then beating on high until fluffy, and add vanilla extract and milk to adjust consistency.