In medium bowl, combine all ingredients except tomatoes and basil sprigs; toss to coat. Cover; refrigerate at least 1 hour to blend flavors.
To make tomato flowers, carefully cut out and discard stem end of each tomato. To form petals, make 6 cuts from top center of each tomato to within 1 inch of bottom, being careful not to cut through bottom. Spread tomato petals slightly.
To serve, spoon half of bean mixture into each tomato. Garnish with basil sprigs.