- Nonstick cooking spray, for the muffin cups
- 2/3 cup cake flour (2.67 ounces, 76 grams)
- ½ cup confectioners sugar (2 ounces, 57 grams)
- ¼ teaspoon salt (1.25 grams)
- ¼ cups blueberries (6.5 ounces, 185 grams)
- 2 teaspoons vanilla extract (8 grams)
- 8 large egg whites (7 ounces, 200 grams), at room temperature
- Pinch of cream of tartar
- ½ cup granulated sugar (3.5 ounces, 99 grams), plus 6 teaspoons additional for sprinkling
- Finely grated zest of 1 lemon
- 12-cup standard-size muffin tin
- Sifter
- Electric Mixer
- Cake tester
- Position a rack in the center of the oven. Lightly grease a standard-size muffin tin with nonstick cooking spray, or use ungreased paper muffin cups.
- Sift the cake flour, confectioners’ sugar, and salt onto a piece of parchment or waxed paper and set aside. In a small bowl, toss the blueberries with the vanilla.
- In a clean bowl of an electric mixer fitted with the whisk attachment, beat the egg whites and cream of tartar on medium-low speed until frothy. Add 1 tablespoon of the granulated sugar and beat at medium until soft peaks form. Beat in the remaining granulated sugar, and raise the speed to high. Beat until stiff peaks form. While the eggs are beating, preheat the oven to 375°F.
- When you have stiff peaks, stop the machine and remove the bowl. Immediately sprinkle the dry ingredients and lemon zest over the egg whites and fold in with a rubber spatula, working carefully to avoid deflating the whites. Fold in half of the blueberries.
- Divide the batter among the muffin cups so that each is two-thirds full. Top each muffin with a few more blueberries and sprinkle each with ½ teaspoon granulated sugar.
- Bake on the center rack until the muffins are lightly golden and a cake tester inserted in their centers comes out clean, 20 to 25 minutes. Remove the muffins from the tin as soon as they come out of the oven and transfer them to a wire rack to cool for 15 minutes. Serve within 4 hours.