What temperature should I serve the Strawberry-Rhubarb Aperitif?

Great question. The strawberry-rhubarb is a bit unique and hard to classify. It has aspects of a dessert wine, which is typically served cold (40-45F).
Since the SR is somewhat less sweet than many dessert wines, the optimum might be a bit higher toward 50F. I have not done a full test yet myself.
As you increase the temperature, the perception of sweetness will probably increase slightly. At the end of the day, I suggest chilling in the frig and
then slowly sipping a glass over time so see where you like it best. Enjoy!