Preheat the oven to 300°F and line a baking sheet with parchment paper.

Drain excess liquid from the cottage cheese, then blend it with a small blender or immersion blender until completely smooth.

In a clean, dry mixing bowl, add the egg whites and cream of tartar and beat with a hand mixer until stiff peaks form.

In a separate bowl, whisk together the egg yolks, blended cottage cheese, cornstarch, powdered sweetener, vanilla bean paste, and lemon zest until smooth.

Gently fold the yolk mixture into the whipped egg whites in 2–3 additions, using a spatula and careful folding motions to keep as much air as possible in the batter.

Add the blueberries and gently fold just until they are evenly distributed throughout the batter.

Use a 1/4 cup measuring cup to scoop mounds of batter onto the prepared baking sheet, spacing them about 2 inches apart.

Bake for 25–30 minutes, or until the cloud bread pieces are puffed, golden brown, and set in the center.

Remove from the oven and let the cloud bread cool on the baking sheet for a few minutes, then transfer to a wire rack to cool completely before serving.