Process the flour, ground almonds, sugar, cinnamon and butter into crumble. Put about 2/3 of the dough in a small springform pan (18 or 20) lined with baking paper and press the dough firmly on, pulling up a small edge (about 1 cm). Put the plum jam on the dough, spread the remaining crumble and the flaked almonds on top. Bake at 180 degrees for about 22-25 minutes. Let the cake cool in the pan.