Philadelphia's tomato pie stands out. What Is a Philadelphia Tomato Pie? A Philadelphia tomato pie is a rectangular piece of flatbread topped with a heavy base of tomato sauce. Trenton Tomato PieNot to be outdone by Philly, Trentonians have something called tomato pie, but it's not the same thing. A proper Trenton tomato pie has the cheese placed first on the dough, finished with a topping of crushed tomatoes.