In a medium saucepan, combine sugar, cornstarch, salt, and ground cinnamon. Stir these together before adding the fresh or thawed rhubarb and lemon juice. Bring the mixture to a boil over medium heat, then lower the heat and let it simmer for about 3 minutes until it thickens. Remove it from the heat and allow it to cool slightly while you prepare the cheesecake layer.

In a large mixing bowl, blend the room-temperature cream cheese and sour cream using an electric mixer on medium speed until completely smooth. Gradually incorporate sugar, and then add the eggs one at a time, mixing thoroughly after each addition. Follow this by adding vanilla extract, taking care not to overmix.

Preheat your oven to 425°F (220°C). Once heated, pour the cooled rhubarb filling into the prepared pie shell, spreading it evenly. Bake for 10 minutes to set the rhubarb layer, then reduce the heat to 325°F (160°C). Pour the cheesecake mixture over the baked rhubarb and return the pie to the oven for approximately 35 minutes, or until the cheesecake is just set and slightly puffed.

After baking, remove the Sweet Rhubarb Cheesecake Pie from the oven and let it cool on a wire rack until it reaches room temperature. Once cooled, refrigerate the pie for at least 4 hours, although overnight is preferable.