Heat oven to 400° F. Coat a 9-inch springform pan, round cake pan, or pie plate with 1 tablespoon of the oil and set aside.
In a medium saucepan, bring 2 1/4 cups water to a boil. Whisking constantly, slowly add the polenta or cornmeal. Reduce heat to low and cook, stirring, until the polenta starts to pull away from the sides of the pan, 4 to 5 minutes. Stir in the salt, 1/4 teaspoon of the pepper, and the Parmesan. Remove from heat.
Spread the polenta over the bottom of the prepared pan, using a spoon to form a raised edge.
In a bowl, combine the radicchio, tomatoes, mozzarella, and the remaining oil and pepper. Spoon the mixture over the polenta. Bake for 30 minutes. Cut into wedges.
Tip: This crisp polenta crust can accommodate almost any pizza topping. Try arugula and prosciutto, sausage and garlic, or caramelized onions and mushrooms.