Cut the potatoes with the skin into not too thick slices. Boil them in salted water until soft and let them steam out.
Preheat the oven to 200 °C.
Wash and dry the tomatoes. Depending on the size, halve or quarter if necessary.
Put them in an ovenproof dish. Mix with olive oil, salt, thyme, sugar and chili. Place in oven for about 15 minutes (or until they pop open).
Fry the potatoes in enough fat until crispy and golden. Drain on paper towels and sprinkle with salt, pepper and thyme.
Fry the steak in a pan with very little oil for about 1 1/2 minutes on each side until medium. Remove and let rest for 3-4 minutes.
Place steak on a plate and sprinkle with sea salt and pepper. Serve with tomatoes and potatoes.