No need to cook macaroni just mix and refrigerate overnight then microwave.

1 can (10 3/4 oz.) condensed cream of celery soup
1 c. milk
1 can (6 1/2 oz.) tuna, drained & flaked
1 c. uncooked elbow macaroni
1 c. frozen green peas
1/2 c. chopped onion
1 c. coarsely shredded Cheddar cheese, reserve 1/4 cup

Whisk soup and milk in 2 quart microwave safe bowl until well blended. Stir in remaining ingredients except reserve 1/4 cup cheese. Cover and refrigerate at least 12 hour or overnight. Cover with lid or vented plastic wrap. Microwave high 15-17 minutes until bubbly. Sprinkle with reserved cheese. Let stand 5-7 minutes until cheese melts.