Preheat your oven to 425°F. Spray a 9-inch round tart pan with non-stick cooking spray and set aside.
In a large mixing bowl, whisk together the flour, cocoa powder, sugar, and 1/2 teaspoon kosher salt. Make a well in the center and pour in the melted butter. Stir until crumbly.
Press the dough into the bottom and sides of the tart pan. Bake for 10 minutes, then let cool for 10 minutes.
In a clean bowl, whisk together the pumpkin, condensed milk, egg, pumpkin pie spice, and 1/4 teaspoon kosher salt until smooth.
Pour the filling into the cooled crust. Bake at 425°F for 10 minutes, then reduce to 350°F and bake for another 25-30 minutes until set.
Let the tart cool in the pan for at least 1 hour before serving.