Preheat oven to 400°.
Arrange polenta slices in an 11 x 7-inch baking dish coated with cooking spray. Combine ricotta cheese, red pepper, spinach, and egg white in a medium bowl. Spread over polenta; spoon marinara sauce evenly over ricotta cheese mixture. Cover with foil; bake at 400° for 30 minutes. Uncover; sprinkle with Parmesan cheese. Bake an additional 5 minutes or until cheese melts. Sprinkle with basil.