Preheat oven to 350 degrees F. Spray a springform pan (8-10 inches) with cooking spray.
In a large bowl, cream together the sugar and butter until smooth and pale. Beat in eggs. Add flour, baking powder, salt, cinnamon, nutmeg, and allspice. Mix until just combined.
Spoon batter into prepared pan, spreading evenly. Arrange plums, cut side down, over top of batter, fitting as many as you can in one layer. Sprinkle top of torte with brown sugar.
Bake in preheated oven for 50-60 minutes, until plums are soft, batter is cooked, and top is golden brown. Remove and let cool before serving.