Cook noodles according to package directions. Meanwhile, in a large skillet, cook beef over medium heat until no longer pink; drain. Stir in taco seasoning. In a small bowl, combine egg white and ricotta cheese. Drain noodles. In 13x9x2 inch baking dish, layer four noodles, 3/4 cup ricotta mixture, half of the beef mixture and 1 1/3 cups cheddar cheese. Top each with four noodles, 3/4 cup ricotta mixture, 1 1/2 cups salsa and 1 1/3 cups cheese. Repeat.
Bake casserole, uncovered, at 350 degrees for 35 to 40 minutes or until heated through. Let stand for 10 minutes before cutting.