Preheat the oven to 350°F (175°C). Prepare an ungreased 10-inch tube pan.
Sift together cake flour, 1/2 cup granulated sugar, and salt at least 3-4 times. Set aside.
In a large, clean, grease-free bowl, beat egg whites until foamy using an electric mixer on medium speed.
Add cream of tartar to the egg whites and increase speed to medium-high. Beat until soft peaks form.
Gradually add remaining 1 cup sugar, 1-2 tablespoons at a time, beating until firm, glossy peaks form.
Fold in fresh lemon zest and vanilla or lemon extract gently.
Gently fold one-third of the sifted flour mixture into the egg whites using an upward motion. Repeat with remaining flour mixture in two additions. Do not overmix.
Toss fresh blueberries lightly with 1 tablespoon all-purpose flour to coat.
Fold floured blueberries gently into the batter until evenly distributed.
Spoon batter into the ungreased tube pan, spreading evenly. Run a knife through the batter to release large air pockets.
Bake for 35-45 minutes until golden brown and a skewer inserted comes out clean.
Invert the pan immediately after baking and cool upside down for 1 1/2 to 2 hours to prevent collapse.
Once cooled, loosen edges with a knife, invert onto a plate, slice with a serrated knife, and serve.