In a stand mixer fitted with the whisk attachment or a hand mixer, beat the pumpkin puree, condensed milk, pumpkin pie spice, salt and egg until smooth. Scrape down the bowl once complete to ensure that everything is evenly mixed.
Pour the mixture over the cheesecake batter and spread evenly. *Avoid using a spatula to spread the mixture as much as possible as to not mix the two layers. Use a measuring cup to pour the mixture throughout the pan to minimize the need to spread it with a spatula.
Bake for 50-60 minutes, or until the center jiggles less easily (you will still see movement when shaking the pan, but the mixture will be slightly firmer).
Remove from the oven and allow it to cool to room temperature, then chill in the fridge for at least 4 hours - overrnight.