Microwave Mac 'n' Cheese Dish

2 C. uncooked elbow macaroni
2 C. hot water
1/3 C. butter or margarine
1/4 C. chopped onion
3/4 teas. salt
1/4 teas. pepper
1/4 teas. ground mustard
1/3 C. all purpose flour
1-1/4 C. milk
8 ounces process American cheese, cubed

In a 2-qt. microwave-safe dish, combine the first seven ingredients.  Cover and microwave on high for  3-1/2 minutes; stir.   Cover and cook at 50% power for 4 minutes or until mixture comes to a boil, rotating a half turn once.
Combine flour and milk until smooth; stir into macaroni mixture.  Add cheese.
Cover and cook on high for 6-8 minutes or until the macaroni is tender and sauce is bubbly,  rotating a half turn once and stirring every 3 minutes.

Makes 4 servings.