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1
Position a rack in the center of the oven.
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2
Lightly grease a standard-size muffin tin with nonstick cooking spray, or use ungreased paper muffin cups.
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3
Sift the cake flour, confectioners sugar, and salt onto a piece of parchment or waxed paper and set aside.
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4
In a small bowl, toss the blueberries with the vanilla.
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5
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.
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6
Add 1 tablespoon of the granulated sugar and beat at medium until soft peaks form.
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7
Beat in the remaining granulated sugar, and raise the speed to high.
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8
Beat until stiff peaks form.
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9
While the eggs are beating, preheat the oven to 375F.
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10
When you have stiff peaks, stop the machine and remove the bowl.
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11
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.
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12
Fold in half of the blueberries.
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13
Divide the batter among the muffin cups so that each is two-thirds full.
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14
Top each muffin with a few more blueberries and sprinkle each with 1/2 teaspoon granulated sugar.
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15
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.
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16
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.
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17
Serve within 4 hours.
