BEFORE YOU GET STARTED: Make sure the cream cheese, sour cream, and eggs are all brought to room temperature or the filling will not mix correctly. DO NOT skip this step
Maintain Oven Temperature of 325 degrees F. Make sure you have a rack arranged in the center of the oven.
Prepare For Water Bath. Start bringing a small pot of water to a boil while you make the cheesecake. Set out a large roasting pan for a traditional water bath or a 9x13 pan for a modified hot water bath (SEE NOTES)
Combine Cream Cheese & Sugar in the bowl of a stand mixer fitted with a paddle attachment, or a large mixing bowl with a handheld electric mixer. Beat the softened cream cheese and sugar together on medium-low speed 2-3 minutes, or until smooth and well blended
Add Eggs One At A Time on LOW Speed, until just barely mixed.
Add Sour Cream, Cornstarch, Lemon Zest, Lemon Juice & Vanilla to the cream cheese mixture and mix on LOW speed until just barely combined. (Keep in mind that you don't want to add any extra air to the cheesecake, so mixing by hand or on low speed at this point is very helpful!)
Stir In Fresh Blueberries. Add 2 cups blueberries and mix them in as gently and slowly as possible so you don't add any extra air. Gently tap the bowl against the counter to help remove any air bubbles.
Pour Filling Over The Crust and smooth the surface with a spatula
Create Hot Water Bath. Carefully pour 3/4 to 1-inch of boiling water into the bottom of the roasting pan. Carefully lower the prepared & wrapped springform pan into the water so the water comes about 1-inch up the sides of the springform pan. (See notes for modified hot water bath instructions)
Bake. Transfer the pan to the oven and bake cheesecake 60-70 minutes or until the edges are just set and the center gently wobbles (like Jello or gelatin). If the center still seems sloshy and liquid, add 3-5 minutes to the bake time and check again. (Err on the side of under-baking rather than over-baking)
Cool 1-Hour In The Oven. When the cheesecake is finished baking, turn OFF the oven heat and crack the oven door open 2-3 inches. Let the cheesecake cool IN the oven for 1 full hour. (To help prevent cracks, you can run a thin knife around the edges of the springform pan before letting it cool.) Remove the springform pan from the hot water bath and the slow cooker liner/oven bag.
Chill Cheesecake Uncovered in The Fridge AT LEAST 4-6 Hours (up to overnight) before decorating.