Best Vanilla Cake

and 3/4 cups (430g) cake flour*

salt

baking powder

baking soda

and 1/2 cups (345g) unsalted butter, softened to room temperature

(400g) granulated sugar

large eggs + 2 additional egg whites, at room temperature*

pure vanilla extract (yes, Tbsp!)

and 1/2 cups (360ml) buttermilk, at room temperature*

and 1/2 cups (345g) unsalted butter, softened to room temperature

(720g) confectioners' sugar

(80ml) whole milk or heavy cream

and 1/2 teaspoons pure vanilla extract

salt