Add the cream cheese, sugar, and cornstarch to a large mixing bowl (or to a stand mixer fitted with the paddle attachment.)
Use a hand mixer (or stand mixer) to beat the ingredients together for 2 minutes, until it's light, fluffy, and free of lumps.
Add the two eggs into the bowl, and beat the mixture on low speed *just* until the eggs have been fully incorporated.
Add in the heavy cream, vanilla bean paste, and lemon juice. Again, beat the mixture on low speed just until cohesive.
Pour the cheesecake batter over the baked shortbread crust. Tap the pan on the counter a few times to help remove air from the batter.
Fill a 9" cake pan, or any larger pan that can reasonably fit the 6" springform inside of it, a third of the way with hot water. Wrap tinfoil around the sides and bottom of your springform pan to help avoid the possibility of water seeping into it.
Place the springform pan into the larger pan, then place the whole thing into the oven. Bake for 60-70 minutes, or until the cheesecake only slightly wobbles and reaches an internal temperature of at least 170°F / 76°C.** If the cheesecake starts to brown on top, gently place a piece of tinfoil over the top of the pan for the rest of the baking time.
Once the cheesecake is fully cooked, turn off the oven and leave the door slightly ajar with the cheesecake in it for 1 hr. Once the hour has passed, cover the cheesecake with plastic wrap and place it in the fridge to chill and set overnight (at least 8 hours.)