Mix all the ingredients of the marinade, brush the meat and let marinate for 1 hour in the fridge. Scrape the tomatoes: cut in their skin and plunge them 30 sec. in boiling water, remove the skin and pips and cut the flesh into small cubes. Salt, pepper. Cover vermicelli with boiling water and let them soften. Drain, rinse with cold water and drain again. Add the cucumber and sliced carrots, minced onion and tomato paste.
Prepare the sauce: mix the lemon juice with the sesame oil, add the nuoc-mâm and chopped coriander.
Brown the cobbles 3 min. on each side, over high heat, then let them rest 2 min. under a sheet of aluminum foil and cut into thin slices. Serve the sliced beef, topped with lime sauce, on a bed of raw vegetable vermicelli.