Coat steak with cornstarch. Cook in a large oiled skillet over medium heat until browned, stirring constantly. Drain the meat on paper towels. Clean the skillet and add the steak and all other ingredients to the skillet. Bring to a boil, cover, reduce heat and simmer for 30 minutes, stirring often. Remove the lid and cook uncovered for an additional 30 minutes or until sauce is thick and meat is tender. Serve with flour tortillas.