2 sticks of unsalted butter, room temperature + more to butter the pans 3 cups gf flour 1 Tablespoon plus 1 teaspoon baking powder ¾ teaspoon salt 1-3/4 cups granulated sugar 2 teaspoons pure vanilla extract 1 cup whole milk 1 8oz. cup gf vanilla yogurt 1 egg yolk 6 egg whites, at room temperature
Place the oven rack in the center of the oven and preheat to 350°F. Grease the bottom and sides of a 13x9 inch baking pan. Line the bottom with parchment paper. Grease the top of the parchment with butter. Lightly flour the bottom and sides of the pan with gf flour. Tap out any excess flour.
In a large bowl, whisk together the gf flour, baking powder and salt. In a large bowl, or the work bowl of a stand mixer, beat the butter on medium speed until smooth, about 1 minute. Add 1-1/2 cups sugar and vanilla extract; continue to beat until well combined and fluffy, about 2 minutes. Stop and scrape down the sides of the bowl. On low speed, add 1/3 of the dry ingredients to the butter mixture; mix until combined. Add half the milk; mix until combined. Continue adding dry ingredients and milk alternating as you go and ending with the dry ingredients. Scrape down the sides of the bowl; add the yogurt and egg yolk; beat for about 30 seconds to make sure everything is thoroughly combined. (The batter will be thick.)
In a separate bowl, beat the egg whites with an electric mixer until soft peaks form. Increase the speed to high and gradually add the remaining quarter cup sugar. Continue beating until the whites form medium-firm peaks. Scoop out about one-quarter of the egg whites and stir into the cake batter to lighten. Gently fold in the remaining egg whites until just blended.
Scrape the batter into the prepared pan. Bake until the top is golden or a toothpick inserted into the center comes out clean, about 30-35 minutes. Set the pans on a rack and let cool for about 15 minutes. Invert the cake onto a rack, lift off the pan and peel away the parchment paper. Let cool completely before frosting.
If you would rather have a round layer cake instead of a sheet cake, the above recipe will make (2) 9-inch round cakes for a layer cake.
We used The Gluten Free Pantry’s Country French bread mix flour for the gf flour in this recipe. To purchase this product please click the link below in our Recommended Tools section.