Ingredients
- 3/4 cup (105 g) all purpose gluten free flour (I used Better Batter)
- 1/4 teaspoon xanthan gum (omit if your blend already contains it)
- 2 tablespoons (18 g) cornstarch (or try potato starch or arrowroot in its place)
- 4 eggs (240 g, weighed out of shell, total) at room temperature, separated
- 1 tablespoon freshly squeezed lemon juice
- 3/4 cup (150 g) granulated sugar
- 1 tablespoon pure vanilla extract
- 9 tablespoons (126 g) unsalted butter, melted and cooled
- 2 cups (16 fluid ounces) warm milk (about 95°F)
- Confectioners’ sugar, for dusting
Instructions
- Preheat your oven to 325°F. Grease well the bottom and sides of an 8-inch square baking dish, and set it aside. In a small bowl, place the flour, xanthan gum and cornstarch, whisk to combine well and set the bowl aside.
- In the bowl of a stand mixer fitted with the whisk attachment, or a large bowl with a handheld mixer, beat the egg whites and lemon juice on medium-high speed until frothy. Add about half of the granulated sugar, and continue to beat on medium-high speed until stiff, glossy (but not dry) peaks form (about 2 minutes). If using a stand mixer, transfer the egg white mixture to another bowl, set the egg whites aside and place the egg yolks, remaining sugar and vanilla in the mixer bowl and beat on medium-high speed with the paddle attachment until well-combined and pale. If using a hand mixer, set the bowl aside, place the egg yolks, remaining sugar and vanilla in a separate, large bowl and beat on medium-high speed until well-combined and pale.
- To the egg yolk mixture, add the melted butter, and beat to combine well. Add the flour mixture and the warm milk to the bowl in three parts each, beginning and ending with the flour and beating until just combined after each addition. The mixture will be thin. Add the beaten egg whites to the batter in three parts, whisking gently to combine after each addition until no obvious white streaks remain. The final cake batter should be light and fluffy. Pour the batter into the prepared pan and place in the center of the preheated oven. Bake until the top of the cake is lightly golden brown and springs back when pressed gently in the center (about 50 minutes). The cake will expand quite a lot in size, but will still be a bit jiggly when shaken gently back and forth. Remove from the oven and allow to cool for at least 15 minutes in the pan before slicing into squares with a sharp knife, while the cake is still in the pan. The cake will shrink on all sides as it cools. Dust lightly with confectioners’ sugar before serving.