Fill a 4-quart saucepan with 3 cups water; add salt and pepper. Cover. Bring to a boil over high heat.
When water boils, reduce heat to medium. Using a whisk or rubber spatula, quickly stir in cornmeal (polenta), cheese, and pesto sauce. Continue stirring until well blended and thick, about 1 minute.
Remove from heat. Pour the cornmeal mixture into an 8-inch pie pan or oven-safe dish. Spread evenly with the back of a spoon. Let stand until firm, about 5 minutes.
Preheat oven to 400 °F. Bake polenta until heated through, about 10 minutes. Remove from oven.