Cut the peppers into pieces, dice the onions. Beat the schnitzel, season with salt and pepper and fry in a little oil until golden brown on both sides, then remove.
Fry the onions and peppers in the frying fat. Dust with the flour and sauté briefly. Deglaze with the vegetable stock and stir in the sour cream. Bring to the boil and season the sauce with salt, pepper, oregano and paprika.
Put the schnitzel in a baking dish, pour the sauce over it and sprinkle everything with the cheese. Gratinate in the preheated oven for approx. 15 minutes at 200 degrees.