Pepperoni Polenta Pizza

Place the polenta, water and salt in a saucepan, and bring to a boil. Cook, stirring constantly for 3 to 5 minutes, until thick. Pour into a pie plate or shallow baking dish. Cover with plastic wrap, and refrigerate until chilled. Preheat the oven to 450 degrees F (220 degrees C). Heat oil in a skillet over medium heat. Add the onion and bell pepper, and cook, stirring until onion is soft. Set aside. Spread the marinara sauce over the chilled polenta 'crust'. Top with the onion and pepper mixture, pepperoni, tomato and oregano. Season lightly with salt and pepper. Bake for 10 minutes in the preheated oven. Sprinkle cheese over the top, and continue to bake for an additional 2 to 3 minutes, until cheese is melted. Cut into 6 wedges, and serve hot.