Preheat oven to 350 degrees F. Coat a half sheet baking pan (18"x13") with baking spray and set aside.
Combine the cake mix, instant pudding mix, eggs, milk, pumpkin puree and 1 tbsp pumpkin pie spice in a large bowl and mix on low speed for 30 seconds. Increase speed to medium and mix for an additional 2 minutes, until light and fluffy.
Spread cake batter in prepared baking pan and bake for 23 to 25 minutes, until cooked through. Let cool completely.
For The Frosting
Combine the cream cheese and butter in a large bowl and beat until light and fluffy. Add in the powdered sugar, vanilla, remaining pumpkin pie spice and pinch of salt. Beat until smooth and incorporated. Add in heavy cream and continue beating until light and fluffy.
Frost cooled cake with cream cheese frosting and enjoy! Keep cake covered and stored in the fridge for up to 7 days.