Combine water, cornmeal and salt in microwave-safe casserole; stir well. Cover tightly with plastic wrap; vent one corner.
Microwave at full power (100 percent) for 10 minutes. Carefully remove plastic wrap. Stir. Cover with paper toweling. Microwave 10 minutes, stirring twice. Pour into greased 10-inch pie pan; cool. Refrigerate until firm, 1 hour.
Sauté sausage, onion and garlic in skillet until sausage is no longer pink, about 8 minutes. Add tomatoes; cook, breaking up tomatoes, for 14 minutes, until slightly thickened.
Heat broiler. Cut polenta into 4 wedges. Place on broiler pan.
Broil 1 minute per side or until lightly browned. Place on serving platter. Pour sauce over and serve. Makes 4 servings.