Slice the onion into half moons. Heat the vinegar, water, sugar and salt in a small saucepan. When the sugar has dissolved, remove from heat and let cool. Place the onion slices in a small jar, pour in the liquid and add the garlic cloves and peppercorns. Store in the refrigerator for 30 min to an hour.
Slice the red cabbage and yellow bell pepper into strips. Slice the cucumber into rounds, then cut them in half. Toast the pita bread briefly in a pan, let it cool down a bit, then cut out the “pockets”.
Heat a bit of olive oil in a frying pan, then add the dumplings and fry them on medium heat for 5-7 minutes, flipping occasionally.
Stuff the pita bread with cabbage, pepper and cucumber, then add the sauce, arrange the dumplings and add the pickled onion at the end.