Cut the meat into approx. 2.5 cm thick slices. Heat the oil in a pan and fry the medallions on each side over medium heat for about 2 minutes. Take out meat.
Peel the onions and cut them into rings. Put in the pan and fry in the frying fat, turning for about 8 minutes. Wash, quarter, core and dice tomatoes. Deglaze onions with cream and stock. Season with salt, pepper and curry and bring to the boil. Stir in the sauce thickener and bring to the boil again. Put medallions in a refractory dish. Spread the onion-cream sauce over it. Sprinkle with tomato cubes and bake in a preheated oven (electric stove 200 degrees) for about 20 minutes. Serve medallions garnished with parsley.