Preheat your oven to 350 degrees Fahrenheit. Grease a 9-inch springform pan thoroughly with butter and line the bottom with a circle of parchment paper to ensure easy removal after baking.
In a medium microwave-safe bowl, combine the chopped bittersweet chocolate and the cubed butter. Heat in 30-second intervals, stirring in between, until the mixture is completely smooth and glossy. Alternatively, you can use a double boiler on the stove for more control.
Whisk the pumpkin puree and granulated sugar into the melted chocolate mixture. Stir until the sugar has mostly dissolved and the mixture looks uniform. Add the alcohol-free vanilla extract and stir again to incorporate the aroma.
Add the eggs one at a time to the batter. Whisk vigorously after each addition until the egg is fully incorporated before adding the next one. This helps create the structure of the torte since there is no flour to hold it together.
Gently fold in the sifted cocoa powder, pumpkin pie spice, and salt using a spatula. Mix until no streaks of cocoa remain, but be careful not to overmix, as you want to keep the batter smooth and airy.
Pour the batter into the prepared springform pan and smooth the top with your spatula. Place the pan on the middle rack of the oven and bake for 35 to 40 minutes. The edges should be set and the center should have a very slight jiggle when gently shaken.
Remove the torte from the oven and place it on a wire rack to cool completely in the pan. As it cools, the center will firm up and the top might crack slightly, which adds to its rustic Christmas charm. Once cool, run a knife around the edges and release the springform sides.
