Add the cottage cheese, lemon juice, lemon zest, sweetener, and vanilla extract to a high-speed blender or food processor.
Blend on high for 1-2 minutes until completely smooth and creamy with no visible lumps.
Add the heavy cream and pulse a few times just until incorporated and the mixture becomes light and fluffy.
Taste and adjust sweetness if needed, then divide between two serving bowls.
Refrigerate for at least 15 minutes before serving for the best texture, or enjoy immediately for a softer mousse-like consistency.