To prepare polenta, place cornmeal in a large saucepan. Gradually add water and 1/2 teaspoon salt, stirring constantly with a whisk. Bring to a boil. Reduce heat to medium; cook 15 minutes, stirring frequently. Remove from heat; stir in grated cheese. Spoon polenta into a 13 x 9-inch pan coated with cooking spray, spreading evenly. Press plastic wrap onto surface of polenta; chill 2 hours or until firm.
To prepare sauce, combine tomato and next 6 ingredients (through pepper) in a medium bowl; set aside.
Cut polenta into rounds using a 2 1/2-inch cookie cutter; coat both sides of rounds evenly with cooking spray. Grill polenta 5 minutes on each side or until golden brown. Serve with tomato sauce, and sprinkle with shaved cheese. Serve immediately.