Cut the meat into thin slices. Mix up the marinade and add the meat, refrigerating for a few hours.
Put a tsp of oil in the frying pan and add the vegetables cooking and stirring. Drain most of the marinade from the meat and add it to the pan as well, bringing to a simmer. Cook over medium heat until the meat is done and the vegetables are soft but still slightly crispy.
On the table put bowls of sour cream, grated cheese, and salsa, as well as some hot tortillas and beans.