Reduce the oven temperature to 325°F.
Whisk together the sugar, flour and pumpkin spice; set aside.
In the bowl of a stand mixer with the paddle attachment, beat the cream cheese and pumpkin puree until smooth and creamy. Scrape down the sides and bottom of the bowl with a spatula. With the mixer running on medium-low slowly add the sugar and spice mixture. Beat until the filling is smooth, scraping down the sides and bottom of the bowl as needed.
With the speed set on medium add the eggs, one at a time, beating just until the yolk disappears before adding the next. Scrape the bowl again and blend on low just until the eggs are incorporated. Don’t over beat the filling.
Add the vanilla and sour cream and blend on low until incorporated. Scrape down the sides and bottom of the bowl and blend again on low for about 5 seconds, or until well mixed.
Pour the batter into the prepared pan. Fill the outer roasting pan with enough hot tap water to come halfway up the sides of the springform pan.
Bake at 325°F until the center jiggles slightly, the sides start to puff and the surface appears dry, about 90 to 100 minutes.
Turn off the oven and prop the oven door open slightly using a pot holder or wooden spoon. Allow the cheesecake to cool in the hot water bath for 1 hour. Transfer the cheesecake to a wire rack and remove the foil. Slide a small thin knife around the inside edges of the pan to loosen the sides of the cheesecake. Leave the cheesecake in the springform pan and cool to room temperature, about 2 hours.
Once cool, cover lightly with plastic wrap and refrigerate overnight or up to 24 hours.
To serve, remove the sides of the springform pan and carefully slide the cheesecake onto a serving platter. Pipe or dollop whipped cream around the outer edges of the cheesecake and garnish with additional pumpkin spice, if desired.
For clean, pretty slices use a large thin knife heated under hot running water. Carefully dry the knife before slicing. Repeat.