Preheat oven to 350°. Cook pasta according to package directions. Meanwhile, in a large skillet, cook beef and onion over medium heat until meat is no longer pink; drain. Add cheese, salsa, tomatoes and taco seasoning. Drain pasta; stir into beef mixture., Transfer to a greased 11x7-in. baking dish. Cover and bake 20 minutes. Uncover; sprinkle with tortilla chips. Bake until heated through, about 10 minutes longer.