Spray bottom of 9x13” baking pan with non-stick cooking spray and set aside (make sure that you only spray the bottom and not the sides).
In a large mixing bowl, combine cake mix, water, vegetable oil, and 3 eggs using an electric mixer. Beat for about 2 minutes on medium speed. Spread cake batter in bottom of pan.
In another large mixing bowl (or you can rinse out the other one and reuse it), mix together pumpkin purée, brown sugar, half-and-half, 3 eggs, pumpkin pie seasoning and salt. Mix together until smooth. Using a large spoon (like a serving spoon), carefully spoon the pumpkin layer on top of the cake layer.
Bake in the preheated oven for 48-53 minutes or until cake doesn’t jiggle when touched in the center.
Remove cake from oven and let cool for at least 30 minutes, then place it in the fridge for 4 hours to chill and set up.
In a large mixing bowl, beat cream cheese, powdered sugar, vanilla, and pinch of salt together until smooth and creamy. Add in whipping cream and beat again until smooth and stiff peaks start to form. Spread topping layer over cake.
If desired, sprinkle top of cake with cinnamon and sugar and serve.