For the rhubarb-apple slices, mix flour with baking powder. Add eggs, sugar, salt and room-warm butter and mix quickly until smooth.
Shape into a ball and let rest in a cool place for 1 hour. Clean rhubarb and pull off strings, cut into pieces about 2 cm in size. Peel apples, cut into quarters, not too finely.
Mix the fruit in a large pot with sugar, cinnamon and a little clove powder. Add 1/8 l water and let it boil over briefly, stir several times, remove from heat and let it steep.
Roll out the shortcrust pastry, pre-bake on the tray in the preheated oven at 200 degrees for 5 minutes on the middle shelf. Then sprinkle with 3-4 tablespoons of breadcrumbs.
Meanwhile, strain the fruit knives, drain well, spread evenly on the pre-baked shortcrust pastry and bake for about 30 min. Finish baking. Let cool.
Take away 500 ml of the drained fruit juice and boil down with 2 pkg. red cake glaze according to instructions. Spread evenly over cake, refrigerate.