Bring milk and salt to boiling in a medium-size saucepan. Pierce sausage links with a fork. Place in a 10-inch deep skillet and cook, covered, over medium-high heat until browned, 10 minutes, turning occasionally.
Meanwhile, stir instant polenta into boiling milk. Cook, stirring, for 3 minutes. Remove from heat and stir in 3 tablespoons grated Parmesan and unsalted butter. Pour onto serving platter, spreading evenly.
To sausages, add sweet pepper strips and stewed tomatoes. Reduce heat to medium, partially cover and cook 5 minutes. Pour mixture over polenta and top with additional grated Parmesan, if desired. Makes 4 servings.