Preheat the oven to 350°F (175°C).

Prepare the pie crust in a 9-inch pie pan and set it aside.

In a mixing bowl, combine the sugar, eggs, and vanilla extract. Whisk until smooth.

Add the heavy cream and ground cinnamon to the egg mixture, blending until combined.

Gently fold in the cranberries into the custard mixture, being careful not to burst them.

Pour the cranberry custard mixture into the prepared pie crust.

Bake in the preheated oven for 40-50 minutes, or until the custard is set with a slight jiggle in the center.

Remove the pie from the oven and allow it to cool completely before slicing.

Serve chilled or at room temperature, optionally topping with whipped cream.