Preheat oven to 425°F. Spray a 9-inch round tart pan with a removable bottom with non-stick cooking spray and set aside.
In a large mixing bowl, whisk together the flour, cocoa powder, sugar and salt. Make a well in the center and add the melted butter. Stir into a crumbly dough.
Press dough into the bottom and up the sides of the tart pan. Place tart pan on a baking sheet and bake crust for 10 minutes. The crust will bubble just a bit as it bakes. Remove and let cool for 10 minutes while you make the filling.
In a mixing bowl, whisk together the pumpkin, sweetened condensed milk, egg, pumpkin pie spice and salt. Pour into crust.
Bake for 10 minutes at 425°F. Reduce oven to 350°F and bake for another 25-30 minutes or until filling is set and a toothpick inserted in the center comes out clean.
Let cool at least 1 hour before serving. Serve with a dollop of whipped cream, if desired.