Clean, wash and quarter the cabbage, cut out the stalk and cut the cabbage into strips. Peel and finely chop the onion. Heat 1 tablespoon of oil in a wide saucepan and fry the onion and cabbage in it while turning.
Deglaze cabbage with 1/8 litre stock and season with salt and pepper. Wash and peel 1 orange so that the white skin is completely removed. Cut the orange into slices. Grate cheese. Wash the meat and dab dry.
Heat the remaining oil in a frying pan and fry the meat on both sides at medium heat for about 3 minutes. Cut the remaining orange in half and squeeze out the juice. Roast almond slivers in a pan without fat.
Take the meat out of the pan, season with salt and pepper, place it on the fat pan of the oven, place a slice of orange on each and sprinkle with the grated cheese. Bake the meat in the preheated oven (electric: 175 °C / gas: level 2) for 12-15 minutes.
Deglaze frying fat in a pan with orange juice and the remaining stock and bring to the boil. Add port wine, stir in sauce thickener, bring to the boil again and season with salt and pepper. Add 3/4 of the almond slivers to the sauce.
Arrange cabbage, sauce and baked turkey filets on a plate, sprinkled with coloured pepper and remaining almond slivers. Serve garnished with parsley if desired.