HEAT oven to 350°F.
PRESS 1 tortilla onto bottom and up side of each of 8 nonstick muffin pan cups. Bake 10 min.
MEANWHILE, cook meat with seasoning mix as directed on package. Stir in 1/2 cup sour cream.
SPOON meat mixture into tortilla cups; top with tomatoes, lettuce, cheese and remaining sour cream.