Add all of the ingredients to a small to medium saucepan. Bring the raspberry mixture simmer over medium to medium-low heat. Don't let it simmer too hard or it will produce a lot of foam.
Cook the raspberry mixture until the raspberries break apart and the mixture thickens, coating the back of a spoon.
Place a fine mesh strainer over a small bowl, and work the raspberry sauce through with a spoon or rubber spatula. Don’t forget to scrape the bottom of the strainer, too. Straining removes many seeds, but some will still remain.
Stir and transfer to a clean, airtight container. Refrigerate up to 20 days; the lemon juice and erythritol in the sweetener will inhibit bacteria.
Makes approximately 2/3 cups or 10 tablespoons with 0.89g net carbs per tablespoon.