Put the bulgur in a bowl and mix with the granulated broth. Cover with boiling water and let steep for about 20 minutes.
In the meantime, hollow out the cucumber and tomatoes and dice them into small pieces. Cut the feta cheese and the onion into small cubes. When the bulgur is lukewarm, mix all the ingredients together. Add salt and pepper to taste, balsamic vinegar and rapeseed oil and mix together. Let the salad stand for about 3 - 4 hours. Then season again to taste.
Season the leftovers with salt, pepper and granulated broth the next day.