Sort the salad, wash and drain. Cut beetroot into thin slices. Mix vinegar with salt, pepper and 1 pinch of sugar. Fold in 4 tablespoons of oil. Slice the parmesan with a peeler into shavings.
Mix butter and fried onions and season with salt. Pat the steaks dry. Cut the fat edge several times with a sharp knife. Put the steaks in a freezer bag and tap them a little thinner. Heat 2 tablespoons of oil in portions in a large pan.
Fry the steaks in it in 2 portions on each side for about 1 minute. Season with sea salt and steak pepper. Reduce heat. Add half onion butter to each portion. Fry for about 1 minute, turning the steaks.
Mix salad mix, beetroot and vinaigrette. Sprinkle with parmesan. Arrange steak on top. Serve with baguette.