Cut phyllo sheets in half crosswise. Working with 1 phyllo sheet half at a time (cover remaining dough to keep from drying), place phyllo sheet on a baking sheet coated with cooking spray. Coat phyllo sheet with cooking spray. Repeat with 2 more layers of phyllo. Sprinkle with 2 tablespoons cheese mixture. Repeat layers 5 times, ending with 2 phyllo sheets. Coat top phyllo sheet with cooking spray; sprinkle with 2 tablespoons cheese mixture. Pat tomato slices with a paper towel. Arrange tomato slices on top of cheese, leaving a 1-inch border. Sprinkle with onions and the remaining 6 tablespoons cheese mixture. Bake at 375° for 20 minutes or until golden. Sprinkle with basil leaves.
Wine note: A good wine for this dish won't overwhelm the delicate phyllo but will stand up to the salty cheeses and fresh basil. A favorite that fills the bill: Veramonte Sauvignon Blanc Reserva from the Casablanca Valley of Chile. The 2008 is $11. —Karen MacNeil