Heat oven to 325°. Line 13x18 half sheet tray with parchment paper; set aside.
Whisk flour, baking powder, and salt in a bowl; set aside. Place sugar and egg yolks in the bowl of a stand mixer fitted with a paddle attachment; mix until it becomes a sandy texture.
Add mayonnaise, milk, buttermilk, green tea simple syrup, matcha powder, and vanilla extract; mix until combined.
Add the dry ingredients and mix just until a batter forms; transfer batter to a bowl and set aside.
Clean stand mixer bowl and add egg whites; replace paddle with whisk attachment. Whip whites until soft peaks form; fold into cake batter.
Pour batter into the prepared sheet pan, smoothing the top with a rubber spatula; drop the pan lightly on a counter to expel large air bubbles. Bake until a toothpick inserted in middle comes out clean, about 15 minutes.
Recipe by Executive Chef Amanda Shook.