Whisk together the salt, baking powder, baking soda, all-purpose flour, pumpkin pie spice, and cinnamon in a mixing bowl.
In a separate bowl, whisk together the pumpkin, melted butter, eggs, vanilla extract, sugar, and brown sugar.
Add the dry ingredients to the wet and mix until just combined using a rubber spatula.
Pour the batter into a greased 8 by 8 baking dish.
Bake the snack cake at 375 degrees for 30-35 minutes, or until a toothpick inserted comes out clean.
Cool the cake completely before frosting it.
To make the frosting, beat together the softened cream cheese and butter, powdered sugar, and vanilla extract until smooth. See notes
Spread the frosting over the cooled cake and cut it into 12 squares.