01 - Preheat oven to 300°F (150°C). Line a baking sheet with parchment paper.
02 - Thoroughly drain cottage cheese to remove excess liquid. Blend cottage cheese in a food processor or with an immersion blender until completely smooth.
03 - In a clean, dry bowl, beat egg whites with cream of tartar until stiff peaks form.
04 - In a separate bowl, whisk together egg yolks, blended cottage cheese, cornstarch, powdered sweetener, vanilla extract, and lemon zest until homogenous.
05 - Gently fold the yolk mixture into the whipped egg whites using a spatula, taking care not to deflate the whites.
06 - Carefully fold in fresh blueberries, distributing evenly throughout the batter.
07 - Scoop 1/4 cup mounds of batter onto the prepared baking sheet, leaving about 2 inches between each mound.
08 - Bake for 25 to 30 minutes or until puffed, golden brown, and firm to the touch.
09 - Allow bread to cool on the baking sheet for several minutes before transferring to a wire rack. Texture will firm as it cools.