For the yogurt sauce, coarsely grate the cucumber and drain on a sieve. Chop the pepper, garlic coriander and mint and mix with some ground cumin through the yogurt. Season with salt and pepper.
Cut the red onion and bell pepper into pieces and peel and chop the garlic. Fry the bell pepper and onion in some oil for a few minutes and fry the garlic briefly.
Fry the marinated pieces in another frying pan according to the instructions on the package. Spoon the through the pepper-onion mixture. Toast the buns in a toaster and cut them open.
Stuff the rolls with some spinach and spoon the mixture on top. Serve with the vegetarian yoghurt sauce.