• Preheat the oven to 350°F. Grease a 9x13-inch metal baking pan.
• In a mixing bowl, combine the flour, cornstarch, sugar, baking powder, baking soda, and salt. Whisk until thoroughly combined.
• Using an electric mixer or a stand mixer with the paddle attachment, slowly beat in the remaining ingredients until combined. Slowly add in the dry ingredients. Increase to medium speed and mix for 2 minutes, or until the mixture begins to lighten in color.
• Transfer the batter to the prepared pan. Tap the pan on the counter a few times to release any large bubbles. Let rest for 10 to 15 minutes.
• Bake for 30 to 35 minutes, or until the internal temperature reaches 200–210°F, or a toothpick inserted in the center comes out clean.

Dairy Free Chocolate Frosting

• In the bowl of a stand mixer, whisk together the egg whites and sugar.
• Set the bowl over a saucepan filled with 2 inches of simmering water. Whisk constantly until the mixture is hot, smooth, and reaches 160°F on a candy thermometer (about 3 minutes).
• Return the bowl to the stand mixer. Whip on medium-high speed until stiff peaks form and the bowl feels cool to the touch (about 5–10 minutes).
• Switch to the paddle attachment. Gradually add the cubed, room-temperature butter and mix until smooth. Add the melted chocolate, vanilla and salt. Mix until fully combined and silky smooth.