Heat the oil in a frying pan and fry the sliced onion until golden brown. Remove and pile onto one side of the ciabatta with the pan juices.Season the steaks and cook over a high heat for 1 minute on each side. Remove to a board and rest for 1 minute. Slice if desired and place on top of the onions.Return the pan to the heat, add a splash or two of red wine or beer, stir well and drizzle over the other side of the ciabatta. Top with the other slice of ciabatta.

Serve with tomato salad.