Preheat oven to 400 degrees.
Melt butter in a sauce pan over low heat. Set aside too cool.
In a mixing bowl, combine rhubarb, sugar, flour and salt. Set aside for 10 minutes.
Prepare single crust pie shell or use a store bought one.
Add rhubarb mixture to the pie shell and bake for 15 minutes.
Using a hand mixer beat eggs until light, creamy and fluffy.
Beat in melted butter, heavy whipping cream.
Slowly add in sugar while beating.
Beat in pure vanilla extract and ground cinnamon.
Once the pie has cooked for 15 minutes, remove from oven. Pour cream mixture into pie shell, filling just to the top of the pie shell. You may have left over cream depending on how deep your pie plate is.
Reduce oven to 350 degrees. Continue to bake pie for an additional 45 minutes or until the top becomes golden brown and the center of the pie is slightly jiggly.
Remove pie and let cool.
Serve cold, room temperature or lightly heated. Enjoy!
This pie must be refrigerated because of the cream custard filling.