Combine tomatoes, lime juice and jalapeno pepper in medium serving bowl; set aside.
Blend avocado, Hellmann's® Real Mayonnaise and sour cream in small bowl with fork until desired consistency. Turn into serving bowl and set aside.
Heat olive oil in medium skillet over medium heat and cook onion, stirring occasionally, until almost tender, about 4 minutes. Add garlic and cook 30 seconds. Add ground beef and chili powder and cook over medium-high heat, stirring occasionally, until ground beef is cooked.
Arrange tortilla chips on large serving plate**, then top with ground beef and sprinkle with cheese. Broil 1 minute OR microwave 30 seconds or until cheese is melted. Garnish with tomato mixture, avocado mixture and, if desired, chopped green onions.