Reduce the oven temperature to 325°F.
In the bowl of a clean food processor, combine ⅓ cup of the sugar with the lemon zest. Pulse until the sugar is pale yellow and the zest is broken down. Transfer the lemon sugar to a 2-cup measuring cup with a spout. Whisk in the remaining 1 cup of sugar and 2 tablespoons flour. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the cream cheese until smooth and creamy. Scrape down the sides and bottom of the bowl. With the mixer running on medium-low, slowly add the lemon sugar mixture. Beat until the mixture 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 down the sides and bottom of the bowl, beat again to blend. Be careful not to over beat.
Add the milk, vanilla and sour cream. Blend on low until combined. Scrape down the sides and bottom of the bowl, and mix again for another 5 seconds or until well blended.
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 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 top edge 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 completely cool, cover tightly with plastic wrap and refrigerate overnight, or up to 24 hours.