Place the strawberries in a medium saucepan over medium heat.
Add the lemon juice, lemon zest, and stevia and mix well.
Gently mash the strawberries with a large fork until desired level of chunkiness is reached. (Alternatively, you could use an immersion blender if a smooth sauce is desired.)
Allow the sauce to come a simmer, then lower the heat to low and continue cooking for about 10 minutes.
Stir in the stevia, then xanthan gum or gluccomannan, mix well, and remove from heat.
Allow the sauce to cool completely before serving over cottage cheese.