Makes 2, 8- or 9-inch cake layers
4 large egg whites / 135 grams
1 cup milk / 242 grams
2 1/2 tsp vanilla (or any extract flavor: almond, lemon, orange, etc.) / 9 grams
1 - 2 tablespoons lemon or orange zest (peel) or 1/8 teaspoon pure citrus oil
3 cups sifted cake flour / 300 grams
4 tsp baking powder / 19.5 grams
1 1/2 cups superfine sugar / 300 grams
3/4 tsp salt / 5 grams
12 Tbsp (1 1/2 sticks) unsalted butter, cut into cubes and then sit out to soften / 170 grams
Preheat the oven to 350 degrees F. Prepare 2, 8- or 9-inch round cake pans with bakers grease or vegetable oil spray and line the bottoms with rounds of parchment or wax paper.
In a 4 cup bowl, combine the egg whites, 1/4 cup milk, vanilla, and orange zest. Beat with a fork to combine. Set aside.
In your mixing bowl combine the flour, baking powder, sugar and salt and mix with the paddle on low speed for 30 seconds to incorporate. Add the butter cubes to the dry ingredients and the remaining 3/4 cup of milk. Mix on low until the mixture is moistened. Scrape the bowl and increase the speed to medium and beat 1 1/2 minutes. Scrape and gradually add the egg white mixture in three batches, beat 20 seconds after each addition, then scrape the bowl each time.
Pour into the prepared pans and smooth the top. Bake 30+ minutes until the top is light brown and springs back when lightly touched. The sides should not shrink back from the pan until after you remove it from the oven.
Remove cake from oven and let cool 10 minutes in the pan, then turn the cake out onto cooling racks. Cool completely and finish with your favorite frosting.