Make the sauce. If using fresh tomatoes, roughly chop them. Place in a pan with the garlic, oil, oregano or marjoram and season to taste. Bring to the boil, then simmer for 10 mins, stirring once or twice. Take off the heat, stir in the basil, then set aside.
When ready to serve, heat a heavy-based frying pan until you can feel a strong heat rising. Smear the oil on both sides of the steak and season each side. Slap the steak into the centre of the pan and adjust the heat to medium-high. Cook for 6 mins, turning halfway through – this is for medium rare. For a medium steak, allow 7-8 mins in total, allow 8-10 mins for well done.
Remove from the pan to a warm platter and leave to stand for 5 mins. Cut in two and serve drizzled with any juices and topped with the sauce.