Drain Pineapple, reserving 1/2 cup juice. Brown beef with onion. Add reserved juice, taco sauce and chili powder. Simmer, uncovered 7 minutes. Arrange shredded lettuce on 4 salad plates. Spoon beef mixture over lettuce. Top with cheese. Arrrange pineapple, avaocado and tomato on salad. Dollop with sour cream. Serve with tortilla chips.