Preheat oven to 350 degrees F. Wrap a double layer of foil around the bottom and side of an ungreased 9-inch springform pan to form a watertight seal; set aside. For crust: In a medium bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add the 1/4 cup sugar; beat until combined. Add flour, cornmeal, and salt; beat until crumbly. Press mixture onto the bottom of the foil-wrapped pan. Bake for 20 minutes. Reduce oven temperature to 325 degrees F.

Meanwhile, for filling: In a very large bowl, combine cream cheese, mascarpone cheese, and the 1-1/2 cups sugar. Beat on medium speed until smooth. Add eggs, lemon peel, and 3 tablespoons lemon juice; beat just until combined. Pour over crust, spreading evenly. Place the foil-wrapped springform pan in a roasting pan. Pour enough hot water into roasting pan to reach halfway up side of springform pan.

Bake for 1-1/4 to 1-1/2 hours or until a 2-inch area around the outside edge appears set and the center appears nearly set when gently shaken. Remove springform pan from water. Cool in pan on a wire rack for 15 minutes. Using a small sharp knife, loosen edge of cheesecake from side of pan; cool completely (about 1-3/4 hours). Remove foil. Cover and chill for 6 to 24 hours.

For topping: In a medium saucepan, combine 2 cups of the blueberries, the 1/2 cup sugar, 3 tablespoons lemon juice, and the water. Cook and stir until mixture comes to boiling. Boil gently, uncovered, for 15 to 20 minutes or until slightly thickened. Stir in the remaining 1 cup blueberries; cook for 2 minutes more. Cool. Cover and chill until ready to serve.

Remove side of springform pan. Spoon topping over each serving of cheesecake. Makes 16 servings.