Remove cream cheese, eggs, milk and sour cream from refrigerator and allow to come to room temperature before preparing this cake (it takes at least 1 hour).
When all ingredients are soft/at room temperature, preheat oven to 350 degrees and lightly butter a 10" springform pan.
Using a standup mixer fitted with a paddle attachment, add softened cream cheese to the bowl and mix a few times. Add sugar; mix until combined. Scrape sides with rubber spatula and mix on low speed until combined.
Add eggs, one at a time, allowing batter to incorporate each before adding another. Scrape sides and continue mixing on low speed.
Add vanilla and flour; mix to incorporate, scrape down sides.
Add milk and sour cream (and lemon zest, if using) and mix until everything is smooth.
Pour mixture into prepared springform pan and place in oven 1 hour.
At 1 hour, turn off heat, open oven door and allow cheesecake to sit in the oven 1 hour.
Remove from oven, cool about 20 minutes, then remove springform pan. Allow to sit at room temperature 1 hour. Best to chill overnight and serve the next day.