1. Preheat oven to 350°.
2. Combine sour cream and cream cheese in a large bowl, stirring until smooth. Stir in taco seasoning. Add beans, stirring until well blended. Spoon mixture into an 11 x 7-inch baking dish coated with cooking spray. Bake at 350° for 10 minutes; sprinkle with cheese, and bake an additional 10 minutes or until cheese melts and dip is bubbly. Top with tomato and green onions. Serve warm.