Preheat the oven to 350°F.
Spray a large sheet pan (13x18x1 inches) with non-stick cooking spray. Set aside.
In a large bowl, whisk together melted butter, milk, pureed pumpkin, sugar, eggs, and vanilla. Whisk until well combined.
In a separate bowl stir together flour, baking soda, cinnamon, pumpkin pie spice, and salt.
Place dry ingredients into wet ingredients and stir just until mixed.
Pour into the sheet pan. Bake for 20 minutes or until a toothpick inserted in the center comes out clean.
Let the cake cool for 15 minutes before icing.
To make the frosting, beat together the butter and cream cheese on high speed until smooth, about 3 minutes.
Add in heavy cream, vanilla, and ground cinnamon and beat on high speed for 2 minutes.
Add in powdered sugar gradually. Beat on high speed for 3 minutes, scraping down sides of bowl frequently.
Spread icing evenly over the cake.