Cook pasta according to package directions to al dente; drain and rinse in cold water. In a large skillet, cook the beef, onion and green pepper over medium heat until meat is no longer pink; drain. In a large bowl, combine the ricotta cheese, 1 cup Italian cheese blend, Parmesan cheese, pesto, egg and half of the beef mixture.
In a small bowl, combine the tomatoes, tomato sauce and Italian seasoning. Spread 3/4 cup into a 13-in x 9-in. baking dish coated with cooking spray. Spoon cheese mixture into pasta shells; place in baking dish. Combine remaining beef mixture and tomato mixture; spoon over shells. Sprinkle with remaining cheese. Cover and refrigerate overnight.
Remove from the refrigerator 30 minutes before baking. Cover and bake at 350° for 40 minutes. Uncover; bake 5-10 minutes longer or until cheese is melted. Yield: 10 servings.