Boil potatoes as jacket potatoes, allow to cool, peel and cut into cubes.
Meanwhile, sauté the onions in a little oil, add the lentils and possibly a pinch of curry, fry briefly, deglaze with the vegetable stock (approx. 200 ml) and cook for 10-20 minutes. If you like it a little hotter, you can also add 1-2 dried chili peppers to the cooking water. But then remove them after the cooking process.
Wash, core and cut the bell pepper and apple. Dice cheese. Crumble black bread. Mix everything. Mix yoghurt, mustard and apple cider vinegar into a sauce and stir well into the salad. Let something go through.