In large bowl, combine tomatoes, green onion, garlic, jalapeno, 1 tablespoon lime juice, and 1/4 teaspoon salt. In 8-inch skillet, heat oil on medium. Add onion; cook 3 to 4 minutes or until golden, stirring. Add chili powder; cook 1 minute. Remove from heat; add beans and 1/8 teaspoon each salt and black pepper. Mash until almost smooth.
In bowl, with fork, mash avocado, cilantro, remaining lime juice, and 1/8 teaspoon salt until almost smooth.
In 1 1/2-quart straight-sided dish, spread bean mixture in even layer. Top with corn and pepper. Spread sour cream and then the salsa over vegetables. Dollop avocado mixture over salsa; spread into even layer. Sprinkle with cheese. Serve immediately, or cover and refrigerate up to 2 hours. Serve with baked tortilla chips.