Cook pasta according to package directions; cover to keep warm.
Combine turkey, pasta sauce, spinach and salt in a 12-inch cast-iron skillet. Cook over medium heat for 3 to 5 minutes or until spinach wilts, stirring occasionally. Stir in cooked pasta. Top with cheese.
Bake for 8 to 10 minutes or until heated through and cheese is melted. Garnish with crushed red pepper, if desired.