Combine 300ml olive oil and 30ml red wine vinegar to make the vinaigrette and set aside.
Heat 30ml olive oil and 30g butter in a heavy-based frying pan.
Cook the steaks for five minutes, turning to color both sides, then remove and rest.
Quickly sauté the tomato quarters, olives, and caperberries in the same pan.
Deglaze the pan with red wine and mix the pan contents into the prepared vinaigrette.
Sauté the pre-cooked potatoes, garlic, and rosemary in olive oil until golden in a hot pan.
Wilt the spinach quickly in a separate hot frying pan.
Serve steaks over spinach and potatoes topped with the tomato and olive vinaigrette.