Combine the raspberries, lemon juice, sweetener and water in a small saucepan. Cook for 5 to 10 minutes, until the raspberries begin to break down.

Taste and add additional sweetener as needed.

Strain in a fine mesh strainer to remove the seeds. Alternatively, you can blend the sauce in a high speed blender.

For a thicker sauce, add ¼ teaspoon xanthan gum.