Preheat your oven to 350°F and lightly grease a springform pan. In a large mixing bowl, beat cream cheese until smooth, then add granulated sugar and flour, mixing until well combined. Gradually incorporate vanilla extract, ground cinnamon, and heavy whipping cream until fluffy. Add eggs one at a time, mixing well after each addition. Bake for 10 minutes at 350°F, then lower the temperature to 200°F and continue baking for 30-35 minutes until set. Cool and refrigerate overnight.

While the cheesecake is chilling, preheat the oven to 350°F for the spice cake. In a separate bowl, whisk together the dry ingredients: flour, baking powder, and spices. In another large bowl, cream together butter and brown sugar until light and fluffy. Add the egg and vanilla, mixing thoroughly. Gradually combine the dry ingredients with the wet ingredients, then mix in the milk until you achieve a smooth batter. Pour into a prepared cake pan and bake for 15-17 minutes. Allow to cool completely and refrigerate overnight.

In a mixing bowl, beat the softened unsalted butter until smooth. Gradually add the powdered sugar, continuing to mix until no lumps remain. Incorporate vanilla extract and heavy cream, mixing until the frosting becomes light and fluffy. Set aside.

Remove the layers from the refrigerator and carefully trim the cheesecake and spice cake layers to ensure uniform sizes. Place the cheesecake on a cake stand, spread a layer of frosting on top, stack the spice cake over the cheesecake, and add more frosting in between. Finally, place the store-bought pumpkin pie on top and frost the entire dessert generously.

Chill the assembled Thanksgiving Piecaken in the refrigerator until the frosting firms up, about 1-2 hours. Once set, slice into generous portions and serve with a sprinkle of ground cinnamon on top.