Tear the lettuce into pieces, pile on a platter and scatter over the beetroot and radishes.
Brush the steaks with oil, then season. Toss the onion in oil. Heat a griddle pan, then cook steaks for 2-3 mins each side, remove and cover with foil to rest. Cook the onions until softened.3 Thinly slice the steaks and arrange over the leaves with the onion and capers. Dress with vinegar and remaining oil, season, then drizzle over soured the cream. Serve with bread.