Preheat oven to 450 degrees F.
Set rack at bottom of oven.
Oil a 10 by 15-inch baking sheet.
In a medium saucepan combine oil, onions, herbs, salt and pepper. Cook about 45 minutes over low heat. Stir frequently to stop onions from sticking. Cook until onions are soft and take on a caramel colour and liquid has reduced completely. Set aside to cool.
Roll out puff pastry to fit baking sheet. Pastry should be rolled out thinly to ensure a crispy crust. Arrange cooled onion mixture evenly over entire surface of dough. Arrange anchovy fillets in a diagonal pattern over top of onions. Add tomato slices and sliced olives. Sprinkle with chopped herbs. Bake 20 minutes or until crisp.