In a medium skillet, cook and stir ground beef and onion over medium-high heat until meat is brown and onion is tender
Drain thoroughly
In a bowl, combine meat mixture, taco sauce, half of the sour cream and salt
Cover and chill for 20 to 30 minutes
To serve, place lettuce on 4 individual plates
Sprinkle with cheese and tomatoes
Spoon meat mixture over salads
Top with remaining sour cream and garnish with olive slices
Serve with tortilla chips