In a medium saucepan, combine the sweetener listed for the sauce with the xanthan gum.
Gradually whisk in water and lemon juice until combined.
Add strawberries and rhubarb and bring saucepan to medium heat, stirring frequently.
Cook mixture until the rhubarb softens (about 4-6 minutes), then remove from heat. Let sauce cool to room temperature before adding to the ice cream.
To make the ice cream, combine heavy whipping cream, vanilla, and remaining sweetener in a large bowl.
Using an electric mixer, whip the mixture until stiff peaks form.
Gradually add the almond milk, blending between each addition. Beat mixture until it re-thickens slightly.
Transfer mixture to ice cream machine and freeze per manufacturer’s instructions.
Once the mixture has reached the creamy texture of ice cream, transfer it to a freezer-safe container. Add the strawberry rhubarb sauce by spooning large dollops on top, then swirling it throughout the ice cream with the spoon. Cool in freezer for 2-3 hours before serving, stirring lightly at 30 minute increments.