Preheat oven to 350 degrees F.
Prepare 1- 8 inch springform pan by greasing and lining bottom with parchment paper.
Have large pan ready to place the 8" pan in for water bath.
Cover the bottom of the pan in heavy duty aluminum foil to stop water from seeping in.
Prepare hot water ahead of time to just about boiling for hot water bath, you will need enough to surround springform pan an inch.
In large bowl with whisk attachment beat cream cheese and sugar until well creamed, about 3 minutes.
Add in cornstarch, mix until combined.
Add in egg one at a time, scraping down side of mixing bowl as needed mixing well with each addition.
Add in lemon juice, vanillas and salt, mix well to combine.
Add in sour cream, mix until all combined.
Pour into prepared pan leaving 1/2 space to account for rising. (you may have a little leftover batter, bake a separate little cheesecake or discard).
Set in larger pan and pour the piping hot water in until the springform pan is surrounded by an inch of water.
Bake 45 minutes.
DO NOT OPEN OVEN DOOR. Turn off oven and let cool for 1 hour in the oven.
Put on rack and cool on counter 1 hour.
Cover and refrigerate overnight.
When ready to remove from springform pan warm the bottom of pan by placing on warm stove top. (I turned on the burner for 30 seconds on high and then turned it off and set the cheese cake on burner for 15 seconds). Wipe sides of pan with hot damp cloth.
With a larger spatula carefully lift slightly and slide onto serving plate. This may take two spatulas, one in front and one in back so the cake does not crack.
Keep chilled until ready to serve.