Preheat the oven to 350°F/175°C (Gas Mark 4). Lightly grease a deep 9-in/23-cm cake pan with butter.

Combine the butter and sugar together in a small saucepan and melt the butter over low heat, stirring to dissolve the sugar, then stir in the stout. Add the orange zest, sultanas, raisins, and candied lemon and/or orange peel. Raise the heat to high, bring to a boil, and boil, stirring frequently, for 3 to 4 minutes. Remove from the heat and set aside to cool.

Sift the flour, baking soda, and pumpkin pie spice together into a large bowl. When the Guinness mixture has cooled to lukewarm, stir it into the flour mixture. Stir in the cherries, then slowly add the eggs, mixing well. Spoon the batter into the pan, and bake for 1½ hours or until done.