Start by preheating your oven to 300°F (150°C) and lining a baking sheet with parchment paper to prevent sticking. In a large mixing bowl, add the egg whites and cream of tartar. Using an electric mixer, whip the egg whites until they form stiff peaks. This step is crucial because the airy texture of the cloud bread relies heavily on properly beaten egg whites.

Next, in a separate bowl, combine the egg yolks, cottage cheese, coconut flour, baking powder, powdered erythritol (if using), and vanilla extract. Mix until fully smooth and creamy. At this point, gently fold the egg yolk mixture into the beaten egg whites using a rubber spatula. It’s important to do this slowly and carefully to avoid deflating the egg whites.

Once the batter is combined, carefully fold in the fresh blueberries. Spoon the mixture into evenly sized dollops onto the prepared baking sheet, leaving some space between each. Bake in the preheated oven for about 25 to 30 minutes, or until the cloud breads are golden and slightly firm to the touch. Allow them to cool slightly on a wire rack before serving.