Place an oven rack on the center shelf and preheat the oven to 350 degrees F. Barely grease the bottom of two 9-inch round cake pans and top with parchment rounds (do not grease the sides of the pan). If you have a sheet pan large enough to fit both cake pans, set them on it to simplify transferring the pans in and out of the oven.
In a medium-sized bowl, whisk together the cake flour, baking powder, and kosher salt. In a separate large bowl, vigorously whisk together the egg whites until frothy, around 15-20 seconds. Whisk in the half-and-half and vanilla extract until evenly combined.
In a stand mixer fitted with the paddle attachment, cream the butter and sugar together on low speed for 3-4 minutes, until the mixture has lightened in color and fluffed up a bit. Scrape down the sides of the bowl.
With the mixer on low speed, swiftly alternate between adding the dry and wet ingredients over 60 seconds, beginning and ending with the dry ingredients. Scrape down the sides of the bowl, all the way to the bottom to catch any hidden dry patches, then turn the speed up to medium for 20-30 seconds to aerate the batter slightly.
Divide the batter equally between the two pans and level the tops out as much as possible (I like using a small offset spatula to do this). Bake for 35 minutes, or until the edges are golden brown, the tops are still slightly pale but firm, and a toothpick comes out clean from the center.
Cool completely, then run an offset spatula or small knife around the edge of the cake to detach any areas that may have stuck. Place a large cutting board or cardboard round covered with parchment (my preference) over the cake pan and gently flip to dislodge the cake. Frost using one of the suggested frostings below (or with your favorite recipe).
Please read my post for a variety of tips and tricks for making this cake!