Heat the oven to 425°F. Lightly coat a 9-inch round tart pan with a removable bottom with nonstick cooking spray, then set it aside while preparing the crust.

In a large mixing bowl, thoroughly whisk together the all-purpose flour, dark unsweetened cocoa powder, granulated sugar, and ½ teaspoon kosher salt.

Create a hollow in the center of the dry mixture and add the melted unsalted butter. Stir until the ingredients come together into a crumbly dough, using your hands for the final mixing if necessary to distribute the butter evenly.

Transfer the chocolate dough to the prepared tart pan. Press it into an even layer across the base and continue pressing it uniformly up the sides.

Set the tart pan on a baking sheet to catch possible drips. Bake at 425°F for 10 minutes. Some bubbling in the crust during baking is normal.

Remove the crust from the oven and allow it to cool for approximately 10 minutes while making the pumpkin mixture.

In a clean mixing bowl, combine the pure pumpkin, sweetened condensed milk, egg, pumpkin pie spice, and ¼ teaspoon kosher salt.

Whisk until the filling is completely blended and has a smooth, uniform consistency.

Pour the prepared pumpkin mixture into the partially cooled chocolate crust.

Bake the assembled tart at 425°F for 10 minutes. Reduce the oven temperature to 350°F and continue baking for another 25–30 minutes.

The tart is ready when the pumpkin center is set and a toothpick inserted into the middle comes out clean.

Leave the tart in its pan to cool for at least 1 hour before slicing. This resting period allows the pumpkin filling to finish setting and makes the tart easier to cut cleanly.