Prepare half the pack of sourdough beforehand (if you use powder, stir it with water and let it steep). Mix rye and wheat flour with salt (not too little). Lightly roast the caraway seeds with the coriander in a pan and break lightly in a mortar or chop with a knife. Add the caraway and coriander mixture to the flour and stir in.
Dissolve the pinch of sugar and the yeast in the lukewarm water. Mix everything completely and knead, form 2 flat loaves and cover and let rest for approx. 10 minutes. Place the 2 loaves of bread on baking paper and brush with water with your hand (so that the crust does not crack too much).
Bake in the preheated oven (250 ° C) for the first 10 minutes and then bake at 180 ° C for about 40 - 45 minutes (total baking time 55 minutes). Let the bread cool down before serving.