The onions are cut into rings and then lightly dusted with flour. Then bake in hot oil until golden brown. Stir frequently. Remove from the oil and drain on kitchen paper.
Season the meat with salt and pepper and dust on one side with flour. Then fry with the flour side in hot oil. Turn, fry briefly, remove and then keep warm.
Deglaze the cooking residue with red wine and reduce. Then pour the beef soup on top and reduce again until you get a nice dark sauce. Season with salt and pepper and assemble with cold butter. If necessary, you can thicken the sauce with a little corn starch.
Put the meat back in the sauce and let it steep for a moment. Arrange on plates, pour the sauce over them and place the lightly salted onion slices on top.