Preheat oven to 350 F.
In a bowl or in a mixer fitted with the paddle attachment, cream butter until fluffy. Add sugar gradually and beat until smooth. Beat in eggs one at a time.
Add sifted baking powder, cream, almond extract and cardamom. Work in flour. Dough will resemble shortbread.
Divide dough into 5 equal parts. Roll dough into rounds, just over 1/4-inch thick. Cut a disc using a 9-inch pan to trace.
Using a palette knife, gently slide disc onto a parchment-lined baking sheet (you should be able to fit 2 discs onto a sheet). Continue rolling and cutting remaining 4 pieces. You may be able to get a sixth layer from scraps. Bake until delicately browned, about 12-15 minutes.
Cover prunes with water in a saucepot and simmer for 10 minutes. Drain liquid, reserving 1/2 cup. Puree prunes in a food processor. Spoon puree back into pot, add reserved liquid and sugar, vanilla and cinnamon. Cook over low heat, stirring regularly, until filling becomes thick. Allow to cool before filling cake.
Alternate cake layers with equal amounts of prune filling, finishing with a top cake layer. To serve, dust top of torte with icing sugar. Refrigerate cake before serving. As the cake chills, the layers will soften.