In a small saucepan, stir together the strawberries, water, stevia extract, and strawberry flavor. Stir in the corn starch and xanthan gym. Place over medium/high heat. Bring to a simmer and keep on the heat for ~10 minutes, or until thickened and strawberries are extremely soft.
Strain the mixture through a fine-mesh sieve. Puree the strained mixture in a blender. Add enough of the natural red food coloring to turn it red. Transfer mixture to a jar, seal tightly, and refrigerate to store. Keeps for ~5 days.
In a shaker cup or blender, add both ingredients and shake/blend until smooth. Enjoy!
**For a paleo version, try ½-1 tsp arrowroot starch.