Use equal amounts of sour cream and cream cheese amount depending upon how many people you want to serve. Same with taco seasoning.
Chop onion, tomatoe,and lettuce. Sit aside
Blend sour cream and cream cheese in a bowl to a dip like consistancy. Whipped cream cheese is easier to work with. Add 1/2 taco seasoning and stir. Add 1/2 of onions and stir. Add shredded cheese being careful to leave some for top.
Pour mixture into a pyrex dish or any oblong container (makes presentation prettier than a bowl). Top with lettuce, tomato, remaining onion, cheese and taco seasoning. Serve with tortilla chips