Preheat the oven to 350°F. Line a 10x15-inch baking pan (jelly roll pan) with parchment paper up the sides.
In a large bowl, whisk together the cake flour, baking powder, and salt. Set aside.
In the bowl of a stand mixer with the paddle attachment, cream together butter, sugar, and both extracts until light and fluffy, about 5 minutes. Stop to scrape down the sides of the bowl as needed.
With the mixer on the lowest speed, carefully add in egg whites, one at a time, beating well after each addition, stopping to scrape down the sides of the bowl as needed.
With the mixer still on low, add ⅓ of the flour mixture into the creamed mixture, then half the milk, another third of the flour mixture, the remaining milk, and then the remaining flour mixture. Mix just until combined. Stop to scrape down the sides of the bowl as needed.
Pour the batter into the prepared pan and bake for 20-25 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cake to cool completely on a wire rack.