Add raspberries, 2 tablespoons water, sweetener, lemon juice, and a pinch of salt to a small saucepan.

Warm over medium heat, stirring often, until the berries release their juices and start to bubble, about 3–5 minutes.

Lightly mash with a spoon or a potato masher to your preferred texture. Taste and adjust sweetener and lemon.

For a thicker sauce without thickeners, simmer gently for 2–4 more minutes to reduce. Stir often to prevent sticking.

Optional xanthan method: Sprinkle xanthan gum very lightly over the surface while whisking constantly. Start with 1/8 teaspoon; add more only if needed. It thickens as it cools.

Optional gelatin method: Remove from heat. Sprinkle powdered gelatin over 1 tablespoon cold water in a small bowl, let it bloom 5 minutes, then whisk into the warm sauce until dissolved.

Stir in vanilla. Remove from heat. For a smooth sauce, press through a fine-mesh strainer to remove seeds. For a rustic sauce, skip straining.

Let cool. The sauce will thicken more as it cools. If it becomes too thick, whisk in a teaspoon of water at a time until it loosens.