Tender and moist, this is the ideal birthday or wedding cake.
Preheat oven to 350°. Line 4 9-inch-round, 2-inch-tall cake pans with parchment and lightly coat with nonstick spray. In the bowl of a stand mixer fitted with the paddle attachment, cream butter and 1¾ cups (350g) sugar on medium speed until pale and fluffy. Use a rubber spatula to scrape bowl well. Add egg yolks 2 at a time, mixing on medium low speed until combined. Scrape bowl well. Add vanilla extract. Sift cake flour, baking powder, and salt into a large bowl. Alternate adding dry ingredients and milk in 3 additions on low speed, starting and ending with dry ingredients. Scrape bowl well. Transfer batter to a large bowl and set aside. In the dry, clean bowl of a stand mixer fitted with the whisk attachment, whisk egg whites on medium speed until frothy. Gradually add 1¾ cups (350g) sugar. Increase speed to high and whisk until mixture becomes a medium-stiff meringue. Test by dipping a spoon into the meringue if it forms a glossy peak the shape of a bird’s beak, it’s ready. Gently fold ½ cup meringue into batter with a rubber spatula to loosen. Continue to fold in remaining meringue with a balloon whisk: cut into the center of batter, then drag whisk toward you and up the side of the bowl. Rotate bowl a quarter turn each time meringue is folded into the batter. Continue to fold meringue in this manner until it is just combined and batter is airy and fluffy. Divide batter evenly between the 4 cake pans. Bake, rotating halfway, until golden brown and a toothpick comes out clean, about 30 minutes. The cake should pull a little from the sides of the pan. Cool completely before unmolding.