Combine sugar and water in a medium saucepan and bring to a boil over medium-high heat. Reduce heat to low and simmer until sugar dissolves, about 3-4 minutes. Cool completely. Place mixture in a covered container and store in refrigerator overnight. Or chill over an ice bath for 30 minutes if you wish to make sorbet right away.
Using a juice extractor, juice 6-8 rhubarb stalks to make 1 and 1/2 cups of juice. When sugar mixture is cool, add rhubarb juice and chopped strawberries; stir to combine.
Pour into freezer bowl of ice cream maker. Turn machine on and mix until mixture thickens, about 25 – 30 minutes. Transfer sorbet to airtight container and place in freezer until firm, about 2 hours.
Serve. Terrific on its own, or serve on top of puff pastry shell, or top with rhubarb sauce.