Preheat your oven to 350°F (175°C).
Prepare the pie crust by placing it in a 9-inch pie dish.
In a large mixing bowl, combine granulated sugar and flour. Mix well.
Add the eggs to the sugar and flour mixture, whisking until combined.
Stir in the heavy cream and vanilla extract, mixing until smooth.
Fold in the cranberries gently so they are evenly distributed.
Pour the cranberry filling into the prepared pie crust.
Bake for 40-45 minutes or until the custard is set and lightly golden.
Let the pie cool at room temperature for at least 1 hour before slicing.
Serve with whipped cream or a scoop of vanilla ice cream if desired.