Grease square baking dish, 8x8x2 inches. Mix cornmeal and cold water in 1 1/2-quart saucepan. Stir in boiling water and salt. Cook over medium-high heat, stirring constantly, until mixture thickens and boils; reduce heat. Cover and simmer 10 minutes, stirring occasionally; remove from heat. Stir in parmesan cheese until smooth. Cool 5 minutes. Spread on bottom and 1 inch up sides of pan. Cover and refrigerate at least 4 hours until completely firm. Heat oven to 350F. Bake cornmeal mixture uncovered in pan 15 minutes. Cook beef in 10-inch skillet over medium heat about 5 minutes, stirring frequently, until brown; drain. Stir in spinach, spaghetti sauce and marjoram. Spoon beef mixture intol polenta shell. Cover and bake 25 to 30 minutes or until heated through. Sprinkle with mozzarella cheese. Bake uncovered about 5 minutes or until cheese is melted. Let stand 10 minutes before cutting. Sprinkle with chopped roma tomatoes, if desired.