Butter the inside of a 2-quart slow cooker using the 1 tablespoon butter; set aside. In a medium bowl whisk together the flour, pumpkin pie spice, baking powder, baking soda, and salt; set aside. In a large bowl, place the 1/2 cup butter; add 1/2 cup boiling water. Whisk until butter melts. Add the sugar, molasses, egg, and zest to the butter mixture and whisk until combined. Add the flour mixture and whisk until smooth.
Spoon batter into prepared cooker. Cover the slow cooker and cook on high-heat setting for 2 1/2 hours (a skewer inserted in the cake comes out with just a few moist crumbs). Remove liner from cooker. Cool 10 minutes in cooker. Invert onto a wire rack. Cool slightly or serve at room temperature sprinkled with powdered sugar and served with whipped cream or ice cream, if desired, and Dried Fruit Compote.
Combine all ingredients in a medium saucepan. Stir in 1 cup water. Bring to boiling; reduce heat. Simmer, uncovered, for 15 minutes or until liquid is syrupy (mixture will thicken as it stands), stirring occasionally. Remove from heat; remove and discard cinnamon stick. Cool slightly or serve at room temperature over Steamed Gingerbread Cake.