Bring a large pot of water to boil for the elbow macaroni.
Add 1 tablespoon salt to water.
Cook macaroni according to package directions until al dente, about 6 minutes.
Drain and rinse.
Spray inside slow cooker with non-stick cooking spray.
Add all ingredients, saving about ¼ cup cheddar, and stir.
Cover and cook on high for 2 to 3 hours, stirring twice.
Sprinkle with reserved cheddar and cover until melted.