Preheat the oven to 375 degrees
Sprinkle the TBSP flour in the bottom of a 9-inch pie pan
Ease the pie crust into the pie pan, crimp the edges, set aside
In a small saucepan add the sugar and cornstarch
Stir to combine
Whisk in the eggnog until smooth
Bring the mixture to a low boil
Reduce the heat and cook for 2 minutes, stir constantly
Remove the saucepan from the heat; add in the butter and extract
Stir until the butter is melted and smooth
Pour the pie mixture into the pie crust
Bake for 25 minutes.
Using a medium bowl, whisk together the sour cream, eggnog, and sugar, until combined and smooth
Remove the pie from the oven
Turn the oven heat up to 400
Evenly spread the sour cream layer on top
Place into the oven and bake for an additional 10 minutes
Remove from the oven and allow to cool
Sprinkle some cinnamon on top