Chop the rhubarb into small pieces (0.5-0.75 inch/1.27-1.9 cm). You can peel the rhubarb first if it’s not pink and tender.
Put the rhubarb, soymilk, and Swerve in a small saucepan. Heat it on the stovetop over medium heat for about 10 minutes, stirring occasionally. The rhubarb should soften and the Swerve should fully dissolve.
Let the rhubarb mixture chill in the fridge for 1-2 hours.
Chop the frozen strawberries and bananas into small pieces if they are large. The smaller you chop them, the easier they’ll blend into smooth nice cream.
Put the chilled rhubarb mixture, frozen strawberries, and frozen bananas in a food processor. Blend until completely smooth. It will take several minutes. You will likely need to stop the processor a few times to scrape down the sides with a spatula.
After it’s completely smooth, you can have your vegan nice cream as a soft serve right away. If it’s too soft, put it in a freezer-safe container and let it freeze for 1-1.5 hours before serving. It should be easy to scoop at that point. If you let it freeze considerably longer, scooping gets harder.
Top your strawberry banana nice cream as desired, and enjoy!