1 1/3 cups all purpose flour
2 tsp baking powder
1/2 tsp ground cinnamon (optional)
1/8 tsp plus a pinch of salt
2 large eggs, separated
1stick unsalted butter, at room temperature
1 cup packed light brown sugar
1/2 cup whole milk
1 pint fresh or frozen (not thawed) blueberries
Confectioner's sugar for dusting
Center a rack in the oven and preheat the oven to 375 degrees. Generously butter an 11-by-7-inch baking pan (a Pyrex pan is great) and place it on a baking sheet.
Whisk together the flour, baking powder, cinnamon (if you’re using it), and the ⅛ teaspoon salt.Working with a stand mixer fitted with the whisk attachment or with a hand mixer in a large bowl, beat the egg whites with the pinch of salt until they form firm, glossy peaks.
Gently scrape the whites into a clean bowl if using a stand mixer. Fit the mixer with the paddle attachment, if you have one. (There’s no need to clean the mixer bowl.) Put the butter and sugar in the mixer bowl, or in another large bowl if using a hand mixer, and beat on medium speed until creamy.
Add the egg yolks and beat 2 minutes more. Reduce the mixer speed to low and add half the dry ingredients, then all of the milk and then the remainder of the dry ingredients, adding each new batch as soon as the previous batch has been incorporated.
Switch to a large rubber spatula and lighten the batter by stirring in about one quarter of the stiffly beaten egg whites. Fold in the rest of the whites, working as gently as you can. Since the cake batter is heavy, it’s only natural you’ll deflate the whites a little — don’t be concerned.
Still working with as light a handle as possible, fold in the blueberries, and scrape the batter into the prepared pan.Bake the cake for 35 to 40 minutes, or until it is golden and a thin knife inserted into the center comes out clean. Transfer the cake to a cooling rack and cool in the pan for about 30 minutes before dusting the top with confectioners’ sugar and serving warm.
Source: Baking From My Home to Yours, 2006