Mix all ingredients for the dough and stir using a food processor or hand mixer for about 10 minutes until a smooth dough forms.
Let the dough rise in a bowl with the lid on or covered with a damp kitchen towel for 2 hours. Tip: I always put the bowl into the oven and just turn on the light. This will keep the dough at the ideal temperature.
After the rising time is up, thinly roll out the dough, and line the large or small baking pan with baking paper. If you have even a small pan, like me, you can divide the dough in half and bake the two cakes one after the other.
Let the dough rise in the pan for another 30 minutes.
In the meantime, wash, pit and cut the plums, see video for how to cut them! At the end of the rising time, evenly distribute the plums onto the dough (see photos) starting from the outside in a circle shape.
Preheat the oven to 200 °C/392 °F top/bottom heat. Now bake the cake for about 30 minutes, until the dough has lightly browned. Depending on the oven, this can take a few minutes longer.
After baking, carefully remove the cake from the tin, remove the baking paper and leave to cool on a rack. This step is very important so that the dough stays nice and crispy, as air comes in from below. If you leave it in the baking pan too long, it the dough will become soggy.
Finally mix the cinnamon and coconut sugar and sprinkle the cake with it.